Humoral Immunity | The B-Lymphocytes | Immunology | Physiology

Summary

This educational video script delves into the intricacies of adaptive immunity, contrasting it with innate immunity. It explains the roles of B lymphocytes and antibodies, including different immunoglobulins like IgM, IgA, IgG, IgE, and IgD, and their functions in humoral immunity. The script also covers T lymphocytes' functions in cell-mediated immunity, the importance of antigen presentation, and the significance of memory cells in secondary immune responses. Moreover, it touches on the lymphatic system's role in immune cell maturation and the major histocompatibility complex's involvement in immune responses.

Takeaways

• 🛡️ Innate immunity is natural and non-specific, providing the first line of defense against pathogens, while adaptive immunity is acquired and specific to particular antigens.
• 🧬 Lymphocytes originate from lymphoblasts, which come from lymphoid stem cells derived from pluripotent hematopoietic stem cells in bone marrow.
• 🏭 B lymphocytes mature into plasma cells that secrete antibodies into body fluids, playing a crucial role in humoral immunity.
• 🔬 Antibodies, or immunoglobulins, are gamma globulins that include different types like IgM, IgA, IgG, IgE, and IgD, each with specific functions.
• 👮‍♂️ White blood cells have various functions, such as neutrophils fighting bacteria and causing pus in acute inflammation, and lymphocytes combating viruses, fungi, and cancer cells in chronic inflammation.
• 🌐 Macrophages are phagocytic cells that aid in fighting foreign invaders and can present antigens, a key process in the immune response.
• 🧬 Adaptive immunity involves both naturally acquired immunity, such as through infection, and artificially acquired immunity, such as through vaccination.
• 💡 Memory B cells and plasma cells are produced when B lymphocytes mature, enabling a faster and stronger immune response upon subsequent exposures to the same antigen.
• 🔑 The major histocompatibility complex (MHC) is essential for antigen presentation to T cells, with MHC class 1 interacting with CD8 T cells and MHC class 2 with CD4 T cells.
• 📚 The lymphatic system is vital for immune function, with lymph nodes serving as sites for lymphocyte training and maturation, and the spleen acting as a filter for blood.
• 🛑 Complement deficiency can lead to increased susceptibility to certain types of infections, with early complement deficiencies affecting resistance to cyanopulmonary infections and late deficiencies affecting resistance to Neisseria infections.

Q & A

What is the main difference between innate immunity and adaptive immunity?

Innate immunity is natural and non-specific, meaning you are born with it and it responds the same way to all foreign invaders. Adaptive immunity, on the other hand, is acquired and specific, meaning it is developed after birth and targets specific pathogens, and it has memory, making the second response stronger and faster than the first exposure.

What does the term 'humoral' in 'humoral immunity' refer to?

The term 'humoral' refers to the body fluids, especially serum and mucous membrane fluids, where B lymphocytes become plasma cells and secrete antibodies to fight invaders.

What are the primary functions of white blood cells as mentioned in the script?

White blood cells have various functions: Neutrophils fight bacteria and are involved in acute inflammation; Lymphocytes combat viruses, fungi, and cancer cells, and are involved in chronic inflammation and adaptive immunity; Monocytes differentiate into macrophages, which are phagocytic and aid in presenting antigens; Eosinophils deal with parasites and are involved in type 1 hypersensitivity; Basophils and mast cells are involved in allergic reactions and type 1 hypersensitivity.

What are the two main types of adaptive immunity?

The two main types of adaptive immunity are humoral immunity, which involves B lymphocytes and the production of antibodies, and cell-mediated immunity, which involves T lymphocytes and the direct destruction of infected or foreign cells.

What is the role of memory B cells and plasma cells derived from B lymphocytes?

Memory B cells remember the specific antigens they have encountered, allowing for a faster and stronger immune response upon re-exposure to the same antigen. Plasma cells secrete antibodies, which are immunoglobulins that help neutralize or mark pathogens for destruction by other immune cells.

What are the five classes of immunoglobulins mentioned in the script, and what are their general functions?

The five classes of immunoglobulins are IgM, IgA, IgG, IgE, and IgD. IgM is involved in the primary response and activates complement; IgA is found in mucous membranes; IgG is the most abundant and crosses the placenta, involved in secondary responses; IgE is associated with allergy and parasite responses; IgD's function is less clear but may be involved in antigen recognition.

How does the immune system distinguish between self and non-self?

The immune system uses antigen-presenting cells (APCs) to display pieces of foreign substances, known as antigens, on their surface using Major Histocompatibility Complex (MHC) molecules. T lymphocytes recognize these antigens presented by MHC and initiate an immune response against the foreign substance.

What is the role of the lymphatic system in immunity?

The lymphatic system is crucial for immune surveillance and filtration. It transports lymph, a fluid containing lymphocytes, through lymph nodes where foreign substances are filtered out and immune responses are initiated. Lymphocytes in the lymph nodes can mature and be activated to fight infections.

What is the significance of the spleen in the immune system?

The spleen acts as a 'police station' for the immune system. It filters blood and houses lymphocytes, including B and T cells, which can respond to blood-borne pathogens. The spleen also contains white pulp, which is rich in lymphocytes, and red pulp, which filters the blood.

What is the function of the complement system in the immune response?

The complement system enhances the ability of antibodies to clear microbes from the body. It can be activated by the classical, alternative, or lectin pathways, and all pathways converge to form the Membrane Attack Complex (MAC), which can directly destroy the cell membrane of pathogens.

Why is the Major Histocompatibility Complex (MHC) important in the immune response?

The MHC is essential for antigen presentation. MHC class I molecules present antigens to CD8 T cells, and MHC class II molecules present antigens to CD4 T cells. This interaction is crucial for the activation of T cells and the subsequent immune response.

Outlines

00:00

🛡️ Innate vs. Adaptive Immunity

This paragraph introduces the concepts of innate and adaptive immunity, focusing on the specificity and memory aspects of the immune response. Innate immunity is non-specific and present at birth, providing the first line of defense without memory. Adaptive immunity, on the other hand, is specific, develops after birth, and includes a memory component that enhances subsequent responses to the same pathogen. The paragraph also discusses the origins of lymphocytes and the different types of white blood cells, their functions, and the distinction between humoral (B lymphocyte) and cellular (T lymphocyte) immunity.

05:01

🧬 B Lymphocytes and Antibody Production

The second paragraph delves into the role of B lymphocytes in the humoral immune response. It explains how B lymphocytes mature into memory B cells and plasma cells, which secrete antibodies known as immunoglobulins. The paragraph outlines the five classes of antibodies (IgM, IgA, IgG, IgE, IgD) and their respective functions, such as opsonization, complement activation, and defense against mucosal pathogens. The importance of antigen presentation by cells like macrophages and the role of the major histocompatibility complex (MHC) in this process are also highlighted.

10:03

🌐 Cellular Immunity and T Lymphocytes

This paragraph discusses cellular immunity mediated by T lymphocytes, which do not secrete antibodies but engage in direct interactions with infected or abnormal cells. It differentiates between T helper cells, which support other immune cells, and cytotoxic T cells, which destroy target cells. The paragraph also covers the regulatory functions of T suppressor cells in preventing autoimmune reactions and the importance of the thymus in T cell maturation. Additionally, it touches on the concepts of antigens, haptens, and the structure of antibodies, including their variable and constant regions.

15:04

🔬 Structure and Function of Lymph Nodes

The fourth paragraph provides an in-depth look at the structure and function of lymph nodes, which serve as filters for the lymphatic fluid and sites for immune cell activation. It describes the organization of B and T cells within the lymph node, the roles of different areas such as the cortex, paracortex, and medulla, and the process of antigen presentation leading to the formation of germinal centers. The paragraph also explains the concept of the lymphatic system and its importance in maintaining immune surveillance and fluid balance.

20:05

🏠 The Spleen and Immune Cell Distribution

The final paragraph examines the spleen's role as another immune organ, paralleling the function of lymph nodes but with distinct structural differences. It details the distribution of B and T cells within the spleen's white pulp and the spleen's role in filtering blood. The paragraph also reviews the major histocompatibility complex (MHC), its two classes, and their interactions with different types of T cells. Additionally, it touches on the complement system, its pathways, and the implications of complement deficiencies on susceptibility to infections.

Keywords

💡Innate Immunity

Innate immunity refers to the body's first line of defense against pathogens, which is present from birth and provides a general defense against a wide range of pathogens. It is non-specific and does not improve upon repeated exposure to the same pathogen. In the script, innate immunity is contrasted with adaptive immunity, highlighting its lack of specificity and memory.

💡Adaptive Immunity

Adaptive immunity is a specialized immune response that develops after exposure to a specific pathogen and includes both humoral and cell-mediated immunity. It is characterized by its specificity, potency, and the ability to develop a 'memory' that results in a faster and stronger response upon subsequent exposures. The video script delves into the mechanisms of adaptive immunity involving B and T lymphocytes.

💡B Lymphocytes

B lymphocytes, or B cells, are a type of white blood cell that plays a crucial role in the adaptive immune response. They mature in the bone marrow and are responsible for producing and secreting antibodies into the serum and mucous membranes to combat pathogens. The script explains that B cells can become plasma cells or memory B cells upon exposure to an antigen.

💡Plasma Cells

Plasma cells are differentiated B cells that produce large amounts of antibodies. They are the source of immunoglobulins, which are proteins that help neutralize or mark pathogens for destruction. The script mentions that plasma cells secrete antibodies into body fluids as part of the humoral immune response.

💡Antibodies

Antibodies, also known as immunoglobulins, are proteins produced by B cells that recognize and bind to specific antigens on the surface of pathogens. They play a central role in humoral immunity by neutralizing pathogens, activating the complement system, and facilitating phagocytosis. The script describes various types of antibodies, such as IgM, IgG, and IgA, and their specific functions.

💡Memory Cells

Memory cells are a special type of lymphocyte that 'remembers' a specific pathogen after an initial immune response. They allow for a quicker and more robust response upon subsequent encounters with the same pathogen. The script emphasizes the importance of memory cells in the adaptive immune system, particularly in the context of B cells maturing into memory B cells.

💡Antigen Presenting Cells (APCs)

Antigen presenting cells, such as macrophages and B cells, are crucial for the adaptive immune response as they display fragments of pathogens (antigens) on their surface using major histocompatibility complex (MHC) molecules. This allows T cells to recognize the antigens and initiate an immune response. The script uses the analogy of a waiter serving food to explain the role of APCs in presenting antigens to lymphocytes.

💡Complement System

The complement system is a group of proteins that enhances the ability of antibodies and phagocytic cells to clear microbes and damaged cells from the body. It can be activated in several ways and ultimately leads to the formation of the membrane attack complex (MAC), which can directly kill pathogens. The script mentions the complement system in the context of its role in amplifying the immune response initiated by antibodies.

💡MHC (Major Histocompatibility Complex)

The major histocompatibility complex is a set of proteins on the cell surface that plays a key role in the immune system by presenting antigens to T cells. There are two classes of MHC molecules, with MHC class I presenting antigens to CD8 T cells and MHC class II presenting antigens to CD4 T cells. The script briefly mentions MHC in the context of antigen presentation.

💡T Lymphocytes

T lymphocytes, or T cells, are another type of white blood cell that is central to cell-mediated immunity. They originate from the bone marrow and mature in the thymus. T cells include various subsets, such as helper T cells, cytotoxic T cells, and regulatory T cells, each with a distinct role in the immune response. The script discusses the different types of T cells and their functions in the immune system.

💡Autoimmune Disease

An autoimmune disease occurs when the immune system mistakenly attacks the body's own cells, tissues, or organs. The script mentions autoimmune diseases in the context of a dysfunction in the regulatory mechanisms of the immune system, such as when T suppressor cells fail to prevent T cytotoxic cells from attacking the body's own cells.

Highlights

Introduction to the difference between innate immunity and adaptive immunity.

Exploration of humoral or B lymphocyte immunity, emphasizing the role of body fluids in antibody production.

Explanation of the origin of lymphocytes from lymphoblasts and their development from pluripotent stem cells.

Discussion on the functions of white blood cells, including neutrophils, lymphocytes, monocytes, eosinophils, and basophils.

Comparison between innate and adaptive immunity, highlighting their specificity, potency, and memory.

Description of naturally and artificially acquired adaptive immunity, including passive and active immunity.

The process of B lymphocyte maturation leading to memory B cells and plasma cells that secrete antibodies.

Detailed classification and function of immunoglobulins: IgM, IgA, IgG, IgE, and IgD.

Importance of the antigen-presenting cell and its role in MHC complex presentation to lymphocytes.

The role of T lymphocytes in cellular immunity, including T helper and T cytotoxic cells.

Function of T regulatory cells in preventing autoimmune reactions by controlling T cytotoxic cells.

The structure of an antibody, including its variable and constant regions, and the hinge region's significance.

Explanation of the complement system and its role in enhancing the immune response.

Overview of the lymphatic system's role in filtering and cleaning the blood.

Description of the lymph node structure and function, including the roles of B and T lymphocytes.

Discussion on the spleen's function as a 'police station' for lymphocytes in the immune response.

Introduction to major histocompatibility complex (MHC) and its two classes, MHC class I and II.

Implications of complement deficiency and its association with specific types of infections.

Transcripts

miracosta's perfixness is here

continuing our physiology playlist in

the last video we talked about the

difference between innate immunity and

adaptive immunity today we will dig

deeper into the topic of acquired or

adaptive immunity talking about humeral

or b lymphocyte immunity what does the

word humor mean it means fluid what kind

of fluid are we talking about your body

fluids especially the serum and the

mucous membrane fluids because your b

lymphocytes will become plasma cells

then they will secrete these beautiful

antibodies into your serum and your

mucous membrane but why to fight those

ruthless invaders this is my physiology

playlist please watch these videos in

order especially the last one as you

know your blood is made of plasma and

cells today's video is talking about the

lymphocytes which are type of the white

blood cells we'll also talk about the

antibodies or the immunoglobulins which

are gamma globulins plasma proteins

where do the lymphocytes come from from

lymphoblasts where the lymphoblasts come

from from lymphoid stem cells which come

from pluripotent hematopoietic stem

cells in the marrow of your bone all of

your antibodies whether you're talking

about igm iga igg ize or igd are gamma

globulins the functions of white blood

cells were discussed before let's review

them very quickly neutrophils fight

bacteria make pus acute inflammation

lymphocytes fight viruses fungi cancer

cells chronic inflammation not acute

chronic they make granuloma adaptive

immunity type 4 hypersensitivity

reactions they are also the cells that

reject organ transplant because they

don't like foreigners monocytes in the

blood are the macrophages in the tissue

macrophages are phagocytic cells they

aid foreign invaders they are also

antigen presenting cells we'll talk

about this today and they can make a

granuloma eosinophils ew disgusting

stuff parasites ill algae ao anaphylaxis

ew type 1 hypersensitivity w basophils

in the blood mast cells in the tissue

they release histamine allergy and type

1 hypersensitivity asthma all kinds of

stuff let's compare between innate and

adaptive innate immunity is natural

meaning you were born with it but it's

very non-specific acquired is adaptive

you were not born with it you have to

acquire it by training and this is

specific like trading with whom training

with the gym trainer i will shut up

training with foreign invaders types of

immunity let's go innate immunity you

were born with it non-specific less

potent present at birth no memory the

first response is the same as the second

response third response etc there is no

difference they respond to foreigners in

the same way like the acid in the

stomach acquired or adaptive immunity

you were not born with it you have to

learn it it is specific the lymphocytes

that target the influenza virus are not

the same as the lymphocytes the target

the pox virus etc etc more potent

developed after birth memory oh i

remember seeing this virus before making

your second response stronger and faster

than your first exposure we're done with

the natural immunity let's dig deeper

into the acquired acquired is naturally

acquired or artificially acquired

naturally acquired you are passive

versus your active your passive you did

nothing you acquired pre-formed

antibodies from your mother through the

placenta or through breast milk either

way you didn't do anything active

naturally acquired is when you get

actually infected now your body will

make brand new antibodies let's talk

about artificial blame your doctor or

thank your doctor passive well you

didn't do anything your doctor gave you

pre-formed antibodies how about active

your doctor gave you vaccines here's the

lymphocyte in the beginning when they

were young they were very naive no

experience whatsoever then they will get

introduced to reality they will have to

fight invaders once they recognize these

foreigners and they deal with them they

will mature they will grow the hell up

they will wise up and they will make

memory cells and they will remember

these organisms so the next time i get

invaded by the same organism the second

response is going to be stronger and

faster and this is called memory does

the innate immunity have memory no the

sequence of events have to be memorized

by you lymphoid stem cells become t

lymphocytes and b lymphocytes let's talk

about the b lymphocytes when they mature

they give you two things memory b cells

and plasma cells let's talk about the

plasma cells plasma cells secrete

antibodies which are immunoglobulins

which are gamma globulins including igm

iga igg ige igd so here's the b

lymphocyte when it was young it was

naive after it got introduced to the

antigen it grew up into mature b

lymphocytes and memory b cells the

material b lymphocytes can become plasma

cell to secrete antibodies each antibody

has two heavy chains

and two light chains when it comes to

the heavy chain you can choose one of

these when it comes to light chain you

can choose one of these for instance

this picture could be an antibody known

as igg kappa b lymphocytes plasma cells

immunoglobulins igm iga igg ige or igd

igg the most abundant like ants it's all

over your body very small therefore can

cross the placenta it's important for

optimization it makes the bacteria tasty

so that you eat it better faster and

stronger ig is responsible for the

secondary response when you see the same

bacteria for the second time who's

responsible for the primary response

then igm it's big it's large it cannot

cross the placenta but it's very good at

fixing and activating complement

remember we talked about complement in

the last video and complement always

ends with the incredible hulk the mac

which will attack all kinds of

foreigners why do you call it complement

because it complements the antibodies

function next we have iga iga is in the

mucosa it decided to leave the

bloodstream and ascend up there into

your mucous membrane mouth nose eyes

ears vaginal canal anal canal etc igd we

don't know the function it's produced

first we'll tell you in next videos that

when the b lymphocyte was naive it only

had two antibodies md it was like a

doctor the naive b lymphocyte is like a

doctor only having an md but then when

it recognizes the antigen when it

matures it can make all kinds of

antibodies it can have m g a d and e

tell me more about them ig the highest

concentration the most abundant

secondary response small what do you

mean by small monomer just one piece

crosses the placenta opsinization it can

activate complement but not as good as

igm also igg has antibacterial functions

antitoxin functions and antiviral

properties example of igg is the rh and

we talked about this in a separate video

in my hematology playlist igm primary

response produced first remember md yup

the naive b them for site was a doctor m

and d produced first produced first it's

very large how many pieces five pieces

pentamer oh that's very large i cannot

cross the placenta but i'm very good at

complement activation igm

complement iga mucous membrane you find

interior saliva wax of the ear vaginal

secretions breast milk etc icd produced

first unknown function maybe antigen

recognition ige disgusting stuff ew

allergy parasites anaphylaxis mast cell

secreting histamine ill

attacks of bronchial asthma if you want

to learn more about the mast cell and

the story of histamine check out my

asthma videos on my pulmonology playlist

the story of immunology this slide and

the next slide are the most important

slides in the entire stinking lecture

it's one of my favorite illustrations

ever here's the deal you have been

invaded by a foreigner like a bacteria

okay

your immune system doesn't need the

entire bacteria i just need a piece

what's the name of that piece antigen

where did it come from from the bacteria

it's a piece of the bacteria thank you

let me introduce this to the immune

cells to tell them that this is

foreigner okay who's gonna carry the

piece antigen presenting cell carry it

on what on something called the mhc

think of it like a waiter bringing you

food who's the waiter antigen presenting

cells okay what's the tray that tray is

the mhc and what is the food the antigen

of the bacteria the customer is always

right who's the customer the lymphocyte

the lymphocyte will recognize the food

or the antigen and then the lymphocyte

will do one of three things or all of

them i can eat the food i will remember

the food and i can become plasma cell to

secrete antibodies only if this is a b

lymphocyte nice let's take a step back

you said that this is the antigen

presenting cell like what it could be a

macrophage a b lymphocyte or langerhan

cell the tray could be mhc class 1 or

mhc class 2. this lymphocyte could be b

lymphocyte or t lymphocyte t lymphocyte

preferred to eat by herself b lymphocyte

prefer to become plasma cell and then to

secrete antibodies and then the

antibodies will destroy the bad food why

do you want to destroy the food because

it's foreigner why do you want to

remember it so that the second exposure

to the same organism or the same toxin

is faster and stronger why do you want

to secrete antibodies well it could be

to fix the complement to bring the

incredible hulk the mac it could be to

defend my mucous membrane which is the

first line of defense anatomically

speaking against invaders it could be to

opsinize the bacteria or to oxidize the

bacterial toxin to make it tasty that i

can eat it faster etc etc and so on and

so forth this story is beautiful this is

the key to understanding the entire book

of immunology so the waiter i mean the

antigen presenting cell presented the

food i mean the antigen the customer i

mean the lymphocyte we have two types of

customers b lymphocytes and t

lymphocytes b lymphocytes secrete

antibodies into the fluids of the body

such as the plasma tears saliva mucus

secretions etc fluids are known as

humors the ancient greeks had a theory

about the four humors water blood yellow

bile black bile anyways humeral means

fluid okay and we have another type of

lymphocyte that cannot secrete

antibodies they prefer face-to-face

interaction i will face that nasty

antigen head-on that's why you call it

cellular immunity or cell-mediated

immunity you're talking about a virus

i'll destroy not just the virus the

virally infected cell i'll destroy the

virus and the cell that the virus has

invaded what's that fungus i'll destroy

the fungus face to face baby

self-mediated immunity what is this

cancer i'll try to kill it face to face

i am not secreting any antibodies into

any fluids this is not who i am why do

you call these b lymphocytes because

they grow in the bone marrow and in

birds they mature in the bursts of

fabricious why do you call these t

lymphocytes because they mature in the

thymus gland tell me more about your t

lymphocytes well we have many types we

have t helper and t size toxic what's

the job of t

cy2 toxic the name has the answer what

does toxic mean

toxic what the cytomean cell toxic

through the cell what kind of cell the

fungus cell the cancer cell the virus

infected cell thank you what's the job

of the t helper the t helper helps all

kinds of cells i will help the t

cytotoxic i will help another type of t

lymphocyte known as the t suppressor or

the t regulatory cell i will even help

the neighbors the b lymphocytes help

them to do what to grow into plasma

cells and secrete antibodies thank you

so much to helper you are impressive

indeed what's the function of the tear

regulatory cell or t suppressor cells

this prevents the t site toxic from

killing your own cells because these t

cytotoxics are crazy they can destroy

your pancreas they can destroy your own

thymus they can destroy your nose cells

muscle cells etc who tells them to stay

away from your own cells t suppressor or

tyrical toy cells stay away from the

self go attack the foreigners what if i

have some kind of problems in my tear

brigatory cells well your t lymphocytes

will attack your own cells in a

phenomena known as the autoimmune

disease such as lupus for example some

definitions what's an antigen it's a

foreign substance that stimulates your

immune system to produce an immune

response why did you call it antigen

because it generates antibody remember

fibrinogen why did you call it

fibrinogen because it generates fibrin

same freaking concept see medicine makes

so much sense once you understand what

the flip you're talking about what's a

happen a heptane is a baby antigen small

enzyme very small molecule on its own

i'm not good enough i cannot generate an

immune response but a hapten which is an

outsider plus a protein which is part of

your body will make an immune complex

that can generate immune response let's

talk about the antibody who secretes the

antibody of the plasma cell where did it

come from from the b lymphocyte where

did the b lymphocytes come from from

lymphoid stem cells in the bone marrow

let's go antibodies here two light

chains and two heavy chains and there is

a beautiful hinge right here and

disulfide bonds connecting the two we

have a variable part and a constant part

the constant part is the same doesn't

change that much all the options all the

actions all the distinctions are here in

the variable portion which is also known

as fab why fab because this is the

portion that binds the antibody to the

antigen it's the fragment for antigen

binding here is the antigen where will

the antigen bind here or here well the

antigen always binds here and this is

the variable part or the fab domain how

about my own cell like my own b

lymphocyte or my own macrophage it's

going to bind here to the constant

region where does the antigen bind here

in the antigen binding site variable

portion epitope is still entered and so

here where does the cell bind like my

macrophage or like my b lymphocyte here

near the constant portion what's the

function of the complement to complement

the action of the antibody and it's

gonna bind here bacteria invaded my body

it's a foreigner let's take a piece

called antigen let me introduce this

who's going to introduce me the antigen

presenting cell like what like a

macrophage b lymphocyte longer hand cell

let's say it's the macrophage the

macrophage recognize the antigen and we

have an antibody here when the antigen

and the antibody meet each other we call

this the antigen antibody complex or

agglutination or clumping now the

macrophage will eat the entire stupid

thing go to hell bacteria how can you

make this entire process stronger bring

in the complement to complement the

action of the antibody don't forget the

first exposure is okay the second

exposure is even stronger and faster

because we're talking about memory here

a more detailed discussion about the

lymphatic system and the anatomy of the

lymph node is found in separate videos

in my hematology playlist why do you

need the lymphatic system all right

here's your heart arteries capillaries

veins okay if the artery has a hundred

percent of the blood the veins only have

ninety percent where did the ten percent

go the ten percent went here to the

interstitial space why do you need that

ten percent for many reasons one of them

is to give them to lymphatic vessels to

do what to clean that blood from any

garbage who's gonna clean the blood

lovely lymphocytes living inside lymph

nodes the lymphocytes are like police

officers they will beat the living crap

out of the bacteria so where is the

police station the lymph node who are

the police officers the lymphocytes who

live inside the lymph node where do

these police officers get their training

and maturation in the police academy if

it's a lymphocyte the police academy is

in the bone marrow if it's a t

lymphocyte the police academies in the

thymus who created the police officers

the bone marrow who are these police

officers lymphocytes where do they live

in the police station which could be

lymph node spleen mucosa associate

lymphatic tissue tonsils etc here's your

lovely lymph nodes fluid is going to

come here nice and we're going to clean

it because we have lymphocytes living

here and then i'm going to give you

clean fluid into the venous system back

to the heart what are these these are

lymph follicles here are your lymph

follicles very nice who lives inside the

follicles b lymphocytes this is the

cortex this is the medulla between the

cortex and the medulla there is the

paracortex who lives in the pericortex t

lymphocytes so cortex has follicles for

the b lymphocytes paracortex is for the

t lymphocytes then the medulla is made

of two pieces middle area cord and

middle area sinus the middle area cord

has plasma cells the middle area sinus

has macrophages love it this is the

cortex which has the follicle all right

when the b lymphocyte was naive we

called it primary follicle when the b

lymphocyte recognized the antigen and

matured we called it the secondary

follicle as a germinal center mental

margin who lives in the follicle b

lymphocytes who lives in the paracortex

t lymphocytes who lives in the middle

early chords plasma cells who lives in

the middle area sinus macrophages why

doesn't you woke professor teach like

this so in the lymph node b lymphocytes

live in the cortex t lymphocytes live in

the paracortex thank you so much let's

leave the lymph node and talk about the

spleen another police station the spleen

has red pulp for blood and white pulp

for cells like white blood cells like

white blood cells all right white blood

cells of course are lymphocytes

including b lymphocytes and t

lymphocytes where do the b lymphocytes

live they always live in follicles where

do the t lymphocytes live in the

periarteriolar lymphatic sheath or pals

so in the lymph node

t cells live in the paracortex in the

spleen t cells live in the pals notice t

lymphocytes always live in something

that start with the letter p so i

invented a woke mnemonic that goes like

this trump pence the t lymphocyte is

always in the p b lymphocyte versus t

lymphocyte who makes them the bone

marrow where do they mature b cells

mature in the bone marrow t cells mature

in the thymus after that they go work in

their police stations lymph nodes spleen

tonsils mucosa associated lymphatic

tissue etc in the lymph node b cells

live in the follicles in the cortex but

in the spleen b cells live in the

follicles of the white pulp these are

peripheral follicles how about t

lymphocytes the t is always in the p so

the b is in the follicle the t is in the

p lymph node paracord in the spleen

p-a-l-s humeral versus cell mediated

pause and review the topic of major

histocompatibility complex was discussed

in a separate video titled human

leukocytic antigen just know that mhc

has two classes class 1 and class 2.

class 1 is in every single stinking

nucleated cell class 2 is only on the

antigen presenting cells such as

macrophages b lymphocyte langerhan cell

these are the two videos that discuss

the topic of mhc you find them in my

rheumatology playlist mhc has two main

classes class 1 and class 2. class 1

interacts with the cd8 t cells class 2

interacts with cd4 cells and there is a

very good mnemonic you always multiply

and the product is always eight my

patient has a big lymph node why could

be reactive due to infection could be a

tumor could be autoimmune snake bite

immunodeficiency and mono now let me

review something that we talked about in

the last video and that was the topic of

the complement system with its three

pathways the only difference among the

three pathways is who started the

cascade who pulled the trigger

regardless of the pathway that you use

the end result is always mac is always

destruction this is the incredible hulk

membrane attack complex a complex of

proteins to attack the membrane of the

bacteria this is your classical pathway

they always end in

the mac alternative pathway the

beginning is different but they always

end with the mac which will attack my

patient has complement deficiency is

this a problem yes it's a problem and it

depends on whether the deficiency is in

the early complement proteins like c1 c2

c4 etc or late complement protein c5 c6

c8 c9 etc if it's early the patient is

at risk of cyanopulmonary infections if

it's late neisseria infections such as

niceria gonorrhea or nycerium meningitis

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