Cell-Mediated (Cellular) Immunity [aka T-cell immunity] - Physiology & Immunology

Summary

In this educational video, Medicosis dives deep into the intricacies of the immune system, focusing on cellular immunity driven by T lymphocytes. The script explains the roles of B lymphocytes in defending against bacteria and T lymphocytes in combating viruses and fungi. It explores the communication between immune cells via cytokines, the significance of MHC in T cell activation, and the importance of recognizing self from non-self to prevent autoimmune diseases. The video also touches on the challenges of organ transplants, the prevention of organ rejection, and the complications of hemolysis, offering a comprehensive overview of immunology.

Takeaways

• 🔬 B lymphocytes mainly defend against bacteria, while T lymphocytes defend against viruses and fungi.
• 🦠 Plasma cells, derived from B lymphocytes, secrete antibodies which neutralize antigens and activate various immune responses.
• 🧪 There are three complement pathways: classical, alternative, and mannose-binding lectin.
• 🧬 Cytokines, such as interleukins, colony-stimulating factors, and tumor necrosis factor, help immune cells communicate.
• 🔗 Antigen-presenting cells present antigens to lymphocytes, which then activate B and T lymphocytes.
• ⚔️ T helper cells (CD4) assist other immune cells, while T cytotoxic cells (CD8) directly kill infected or cancerous cells.
• 🔄 Major Histocompatibility Complex (MHC) molecules present antigens to T cells; MHC class I activates CD8 cells and MHC class II activates CD4 cells.
• 🧠 Immunodeficiency, such as AIDS caused by HIV, weakens the immune system by attacking CD4 cells.
• 🤰 The placenta acts as a barrier between mother and fetus, preventing maternal immune attack on the fetus.
• 🩸 Successful tissue or organ transplants require matching donor and recipient MHC and immunosuppressive therapy to prevent rejection.

Q & A

What is the main difference between humoral immunity and cell-mediated immunity?

Humoral immunity, primarily mediated by B lymphocytes, defends the body against bacteria through the secretion of antibodies in the body's fluids, while cell-mediated immunity, primarily mediated by T lymphocytes, involves direct cell-to-cell interactions to destroy infected cells, such as those affected by viruses, fungi, or cancer.

What are the three types of cytokines mentioned in the script?

The three types of cytokines mentioned are interleukins, colony-stimulating factors (CSF), and tumor necrosis factor (TNF).

How do antigen-presenting cells (APCs) interact with T lymphocytes?

APCs interact with T lymphocytes by presenting antigens on their surface using major histocompatibility complex (MHC) molecules. MHC class I is used for activating CD8 T cells, while MHC class II is used for activating CD4 T cells.

What is the role of T helper cells in the immune response?

T helper cells play a crucial role in activating other immune cells, such as B lymphocytes, to produce antibodies or become memory cells, enhancing the immune response to subsequent exposures to the same antigen.

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

The immune system distinguishes between self and non-self through several mechanisms, including energy depletion to weaken potentially harmful self-reactive lymphocytes, deletion of strongly self-reactive T cells during maturation in the thymus, and the action of T regulatory cells that suppress self-reactive immunity.

What is the significance of the term 'humoral' in humoral immunity?

The term 'humoral' in humoral immunity refers to the fact that antibodies are secreted into the body's fluids, such as serum or mucous membranes, to combat pathogens.

What is Acquired Immunodeficiency Syndrome (AIDS) and what causes it?

AIDS is a syndrome characterized by a weakened immune system due to the infection with the Human Immunodeficiency Virus (HIV), which is an RNA virus. HIV-1 is the more common and global type, which primarily attacks CD4 helper T lymphocytes, impairing the immune system's ability to fight infections and diseases.

What is the role of Human Leukocyte Antigen G (HLA-G) in pregnancy?

HLA-G, unique to pregnancy, is secreted by the placenta and helps prevent the mother's immune system from attacking the fetus by inducing a state of immunodeficiency that is protective for the survival of the fetus.

Why are live attenuated vaccines not recommended for pregnant women?

Live attenuated vaccines are not recommended for pregnant women because their immune systems are already in a state of immunodeficiency to protect the fetus. The live microorganisms in these vaccines could pose a risk to both the mother and the developing baby.

What are the complications of hemolysis after a blood transfusion?

Complications of hemolysis include hyperkalemia, hyperphosphatemia, and kidney damage due to the release of potassium, phosphate, and hemoglobin from burst red blood cells. Hemoglobin can also cause kidney failure and hemosiderin in the urine.

How can organ rejection after a transplant be prevented?

Organ rejection can be prevented by matching the donor and recipient for blood and HLA types before surgery, and by using immunosuppressants after surgery to suppress the recipient's immune system and prevent it from attacking the transplanted organ.

Outlines

00:00

🧬 Cellular Immunity and T Cell Functions

This paragraph introduces the concept of cellular immunity, focusing on T lymphocytes' role in defending the body against viruses and fungi. It explains the difference between B lymphocytes, which produce antibodies to combat bacteria, and T lymphocytes. The explanation covers how antibodies neutralize antigens, the process of opsonization, agglutination, and activation of the complement system. It also delves into how immune cells communicate through cytokines, specifically interleukins, colony-stimulating factors, and tumor necrosis factors. The paragraph concludes with a review of immunology, detailing the process of antigen presentation, lymphocyte activation, and the development of memory cells for a faster and stronger immune response upon subsequent exposures to the same antigen.

05:03

🛡️ Major Histocompatibility Complex and Immune Activation

The second paragraph delves into the activation of T cells by antigen-presenting cells (APCs) through the Major Histocompatibility Complex (MHC). It discusses the importance of MHC class 1 and class 2 in activating CD8 and CD4 T cells, respectively. The paragraph also touches on the concept of signal one and signal two in T cell activation, involving interactions between CD80/86 and CD28. The explanation extends to the role of T helper cells in supporting the immune response and the function of T regulatory cells in preventing autoimmune reactions. Additionally, it covers the basics of Acquired Immunodeficiency Syndrome (AIDS), caused by the HIV virus, which targets CD4 helper T lymphocytes, leading to a weakened immune system.

10:03

🚫 Autoimmune Diseases and Transplant Rejection

This paragraph explores the mechanisms that prevent the immune system from attacking the body's own cells, such as energy depletion and deletion of self-reactive T cells during thymic maturation. It also explains the role of T regulatory cells in suppressing the immune system to avoid autoimmune diseases. The paragraph then discusses the complications of autoimmune diseases, including type 1 diabetes, myasthenia gravis, celiac disease, and rheumatoid lupus. Furthermore, it addresses the challenges of tissue transplants, such as organ rejection due to MHC incompatibility, and the measures taken to prevent it, including matching donors and recipients and using immunosuppressive drugs.

15:04

🩸 Hemolysis and Its Complications

The final paragraph discusses the consequences of hemolysis, the rupture of red blood cells, which releases potassium, phosphate, and hemoglobin into the bloodstream. This can lead to hyperkalemia, hyperphosphatemia, and a decrease in calcium levels due to the solubility product relationship. The paragraph also explains how the accumulation of hemoglobin in the kidneys can cause kidney damage, leading to kidney failure and hemosiderinuria. It concludes with a reminder of the importance of blood screening to prevent the transmission of infections and a call to support the creator's educational efforts.

Keywords

💡Cellular Immunity

Cellular immunity, also known as T cell immunity, is a type of immune response that involves T lymphocytes defending the body against intracellular pathogens such as viruses and fungi. In the video, the concept is introduced as the main focus of the episode, contrasting with humoral immunity which involves B lymphocytes and antibodies.

💡T Lymphocytes

T lymphocytes, or T cells, are a type of white blood cell that play a central role in cell-mediated immunity. They can be divided into T helper cells (CD4+) and T cytotoxic cells (CD8+). The script explains that T cells are crucial for recognizing and destroying infected cells and coordinating the immune response.

💡Antigens

Antigens are substances recognized by the immune system as foreign, triggering an immune response. In the video, antigens are described as pieces of foreign bacteria that are presented to lymphocytes to initiate an immune reaction.

💡Cytokines

Cytokines are small proteins that act as messengers in the immune system, facilitating communication between cells. The script humorously describes cytokines as 'the internet of leukocytes,' highlighting their role in cell signaling and immune regulation.

💡Major Histocompatibility Complex (MHC)

MHC is a set of proteins on the cell surface that present antigens to T cells. The video explains the importance of MHC class I and class II in activating CD8+ and CD4+ T cells, respectively, and their role in the immune response.

💡Acquired Immunodeficiency Syndrome (AIDS)

AIDS is a syndrome caused by the HIV virus, which leads to a weakened immune system. The script discusses how HIV primarily targets CD4+ T helper cells, impairing the immune system's ability to fight infections and diseases.

💡Autoimmune Diseases

Autoimmune diseases occur when the immune system mistakenly attacks the body's own cells. The video mentions conditions like type 1 diabetes and myasthenia gravis as examples, illustrating the consequences of the immune system's failure to distinguish self from non-self.

💡T Regulatory Cells

T regulatory cells, formerly known as T suppressor cells, help to suppress the immune system's response to prevent autoimmune reactions. The script explains their role in maintaining immune tolerance and preventing the immune system from attacking the body's own cells.

💡Human Leukocytic Antigen G (HLA-G)

HLA-G is a unique form of the major histocompatibility complex protein expressed during pregnancy. The video describes its role in protecting the fetus from the mother's immune system, highlighting its importance in successful pregnancy outcomes.

💡Organ Rejection

Organ rejection occurs when the recipient's immune system recognizes a transplanted organ as foreign and attacks it. The script discusses the importance of matching donors and recipients based on HLA types and using immunosuppressive drugs to prevent rejection.

💡Hemolysis

Hemolysis is the rupture and destruction of red blood cells, which can release harmful substances into the bloodstream. The video explains the complications of hemolysis, such as the release of potassium and hemoglobin, which can lead to kidney damage.

Highlights

Introduction to cellular immunity or T cell immunity, contrasting with B cell immunity.

Explanation of how plasma cells secrete antibodies, derived from B lymphocytes.

The process of neutralization, opsonization, agglutination, and activation of the complement system by antibodies.

Communication between immune cells via cytokines, categorized into interleukins, colony-stimulating factors, and tumor necrosis factor.

The role of T helper cells in activating B lymphocytes to produce antibodies or memory cells.

Differentiation between humoral immunity involving antibodies in body fluids and cell-mediated immunity involving direct cell-to-cell interaction.

Identification of T lymphocytes by their cluster of differentiation (CD) markers.

The function of T helper cells in supporting other immune cells and maintaining immune system balance.

The role of T cytotoxic cells in targeting virus-infected cells, fungi, and cancer cells.

Mechanisms of T cell activation involving antigen-presenting cells and MHC (Major Histocompatibility Complex).

Importance of the second signal in T cell activation, involving CD80/86 and CD28 interactions.

Definition and explanation of Acquired Immunodeficiency Syndrome (AIDS), its transmission routes, and the role of HIV.

The significance of the placenta in preventing maternal immune response against the fetus during pregnancy.

Overview of the mechanisms that prevent the immune system from attacking the body's own cells.

Discussion on autoimmune diseases, such as type 1 diabetes, myasthenia gravis, and celiac disease, caused by the immune system attacking self-antigens.

Importance of matching donors and recipients in organ transplants to prevent immune rejection.

Strategies to prevent organ rejection, including immunosuppressive drugs and total lymphoid irradiation.

The process of blood transfusion compatibility and the risks associated with incompatible blood types.

Complications of hemolysis, including hyperkalemia, hyperphosphatemia, and kidney damage.

Historical context on blood transfusion methods and advancements in preventing air embolism.

Call to action for viewers to support the channel and access additional educational resources.

Transcripts

what's going on everybody is medicosis

perfectionist where medicine makes

perfect sense let's continue our

physiology playlist in the last video we

talked about the hemorrhagial immunity

or the b cell immunity today it's time

to talk about the cell mediated or

cellular immunity or t cell immunity b

lymphocytes mainly defend your body

against bacteria but t lymphocytes

defend your body against viruses and

fungi joe rogan may relate now let's get

started who secretes antibodies plasma

cells where did they come from from b

lymphocytes what happens when your

antibody meets the foreign antigen

neutralization of the bad antigen

opsinization make it tasty agglutination

activation of the natural killer cell to

kill those bacteria and activation of

the complement system remember the

antigen antibody complex activates the

classical pathway of the complement we

have three complement pathways number

one the classical pathway number two

alternative pathway number three mannose

binding lectin pathway how do your

immune cells such as the lymphocytes

communicate with each other they release

cytokines what does cyto mean cell

because they are talking to each other

and they are cells kinds from kinetic

motion oh some secreting chemicals to

put these cells in motion love it here

is the most basic idea of cytokines they

are divided into three categories

the interleukins colony stimulating

factors and tumor necrosis factor ilcsf

tnf what does inter mean between look

leukocytes or white blood cells i n is a

protein or peptide or whatever so

interleukin literally means the internet

of the leukocytes i love it this is how

they communicate with each other colony

stimulating factors factors that

stimulate the colony of the white blood

cells for example and if you remember my

previous videos we talked about gcsf and

gm csf granulocyte colony stimulating

factor and granulocyte monocyte colony

stimulating factor let's review the

story of immunology here is a foreign

bacteria invading your body we'll take a

piece of it the piece is called the

antigen and then who's gonna present the

antigen antigen presenting cells duh

presented to whom to the lymphocytes and

when the lymphocytes recognize the

antigen they will stop being so naive

and they will grow the french toast up

grow to do what to destroy the microbe t

lymphocytes especially the t helper

cells are going to activate the b

lymphocytes so that the b lymphocytes

become plasma cells to secrete

antibodies or to become memory cells so

that we can remember this interaction so

that the second exposure to the same

antigen is gonna be faster and stronger

we're gonna kick that bacteria in the

butt as you know the antigen presenting

cells could be a macrophage a v

lymphocytes or a dendritic cell b

lymphocytes hemorrhal immunity t

lymphocytes cell mediated immunity why

do you call this femoral immunity

because we're secreting antibodies in

the humors the fluids of the body such

as the serum or your mucous membrane

fluid why do you call this cell mediated

because the cell by itself is gonna go

and kill this stupid virus face to face

cell to cell that's why it is cell

mediated the t lymphocytes could be t

helper cd4 or t cytotoxic cd8 the

cluster of differentiation is like your

identification card how does the police

recognize adam by his id okay how do you

recognize the type of the lymphocytes by

their cd the t toxic side to toxic toxic

to cells i'm toxic to fungi virus

infected cells and cancer cells but t

helper is of huge help i can help my

sister i can help my brother i can help

my neighbor okay tell me about your

sister the t-shirt toxic i am cd4 she's

cd8 she's my sister we're very close

both of us have cd3 as well okay why

would you help the t-cell toxic to kill

foreigners and cancers how do you help

your brother i help the t regulatory

cell formerly the t suppressor cell

suppress my own immunity a little bit so

that i do not attack my own cells so

that i gain tolerance to the self

otherwise i will get autoimmune diseases

how do you help your neighbor i will

help my neighbor the bay lymphocyte to

mature and grow the french toast up so

that it can become memory cell to

remember the same bacteria when she

comes again next time or to become

plasma cells to secrete antibodies into

the fluids of my body let's activate the

t cell what's that the antigen

presenting cell presenting what the

antigen or the food to the t lymphocyte

and what's the tray on which you put the

food mhc okay

if we are activating

cd8 we will use mhc class 1 but if we

are activating cd4 t lymphocytes we will

use mhc2 so that the product is always

8. mhc class 1

will activate cd8 t cells and mhc class

2 will activate cd4 cells the result is

8. okay so now i know that the mhc major

histocompatibility complex will interact

with the t cell receptor which is a

receptor on the t lymphocyte imagine my

shock but why did we call it major

histocompatibility complex major because

it's a major group of proteins and there

is another group called minor complex

because it's more than one protein

histocompatible i love it compatible

with my own tissue and that's why when i

saw the bacteria this was not compatible

oh it's about compatibility then you got

it what's that this is the id of the

lymphocyte i could be cd4 or cd8 whether

i'm cd4 or cd8 i'll also have the cd3 id

this is the first signal the second

signal is cd 8086 from the antigen

presenting cell with cd 28 from the t

lymphocyte everything here is eight 80

86 28. they will interact together so

here is signal number one and here is

signal number two that's why we call

this signal and co signal or co

stimulation

cd8086 has another name b7 protein why

b7 the way i remember it is that the

antigen presenting cell could be a b

lymphocyte right yeah it's easy to

remember 7 28 8086 what is acquired

immunodeficiency syndrome or aids it's a

syndrome which means more than one

symptom affecting the same person

immunodeficiency my immune system is

weak deficient acquired because it's not

inherited it's not congenital i'm not

born with it most of the time i acquire

it later in life whether it is through

inner course parental transmission by

injections vertical transmission from

mommy to baby while passing through the

vaginal canal during delivery or from

mommy to baby via breastfeeding this is

the name of the disease and i've just

told you about the route of transmission

but what's the cause oh the infectious

particle is hiv virus which is an rna

virus there are two types of this or two

major types hiv-1 and hiv2 which one is

more common hiv-1 which one is more

global

hiv-1 it's gonna attack my cd4

helper t lymphocytes and therefore i

cannot help my sister and i cannot help

my neighbor i cannot kill virus

virus-infected cells and i cannot

secrete antibodies that's why my

immunity is frail another important

point mom is different from the baby

their genetic material is different and

they are immunologically different and

that's why the placenta is so important

the placenta acts as a barrier between

the mother and the fetus to prevent the

mixing of blood between the maternal and

the fetal sides and in order for mommy

not to attack her baby the pregnancy

will induce a state of

immunodeficiency which is protective for

the survival of the fetus that's why we

do not give pregnant women live

attenuated vaccines because their

immunity is already weak and live

attenuated vaccines contain the live

microorganism or the life agent this

could be dangerous during pregnancy

moreover the placenta secretes human

leukocytic antigen g have you ever heard

of g no i've heard of hla a b c which

are part of mhc1 and hlad which is part

of mhc2 i've never heard of hlag yup

this is unique to pregnancy and g stands

for gestation do you want your immune

system to attack and destroy foreign

invaders abso freaking lootly do you

want your immune system to attack your

own cells oh heck no if my immune system

attacks my own cells i will get an

autoimmune disease which is horrible

then how come normally speaking your

immune system does not attack your own

cells how did the immune system tell the

difference between the self and the

non-self jazillion mechanisms i'll just

give you three number one colonel energy

those two lymphocytes that might get

crazy and attack my own cells will just

make them weak will weaken them and no

energy from energy like no energy all

the t lymphocytes will be stupid and

lazy so that they do not attack my own

antigens how about the one that are

super strong against my own cells delete

them destroy them wipe them out where

did the t lymphocyte mature in the

thymus okay i will destroy it there also

the t regulatory cells formally t

suppressor cells will suppress my own

immunity just a little now what if i

fail to do all of this your immune

system is gonna attack your own cells

creating auto antibodies and this is

called an autoimmune disease such as

type 1 diabetes where you have

antibodies attacking your own pancreas

especially the beta cells which make

insulin myasthenia gravis you have

antibodies attacking your own nicotinic

sub m receptor on the skeletal muscle

that's why these patients are weak we

also have celiac disease which is auto

antibodies against tissue

transglutaminase iga in the small

intestine

rheumatoid lupus and others there are

other topics that you need to know when

it comes to the physiology of the blood

and the immune system and this is the

incompatibility and the rh

incompatibility they were discussed in

great detail in my hematology playlist

right here on youtube let's talk about

tissue transplant okay here is adam's

kidney right adam is donating a kidney

to sarah because sarah needs a kidney as

you might have noticed adam is different

from sarah well no duh adam has a

different mhc than sarah yeah its major

h2 compatibility of course was

compatible with adam might not be the

same as what's compatible with sarah

thank you captain obvious can this be a

problem absolutely adam gave his kidney

to sarah but sarah recognized the kidney

as foreign to her and started attacking

the kidney and destroying the kidney

after the transplant surgery i don't

recognize this kidney this is just some

caring behavior right there hey

mithicosis why are you attacking

patients so much why don't you have some

respect for yourself yes ma'am i was

just joking so how do we prevent this

how do we prevent this organ rejection

well before surgery we have to do some

stuff and after surgery we have to do

some stuff before surgery match the

donor with the recipient how do i do it

groups make sure they match our age

groups make sure that they match and hla

matching and then you prepare the

patient by suppressing the patient's

immunity so that the patient's immune

system does not attack the new kidney

and immunosuppressants include

glucocorticoids or steroids cyclosporine

cyrolimus tacrolimus

antithymocyte globulins etc if it is so

severe total lymphoid irradiation we

will destroy sarah's lymphoid organs so

that they do not secrete crazy

lymphocytes that attack the new kidney

these medications are not the same they

have different indications different

side effects etc and this was discussed

in my course called anti-cancer

pharmacology available to download on my

website medicosisperfectsnation.com

blood

same concept applies before you give

blood from a donor to a recipient match

them make sure they are compatible with

each other because if they are not

compatible bad things can happen antigen

antibody reaction destroying the red

blood cell too it's gonna rupture

causing hemolysis and hemolytic anemia

also these complexes can clog vessels

causing ischemia and pain historically

before we used plastic bags for blood we

used to use glass bottles the blood will

run out and then air bubbles will go

from the bottle to the patient's blood

causing air embolism but now the plastic

bags they will just recoil after the

last drop of blood preventing air

embolism this is huge if you gave the

patient some dirty blood you might

introduce infections that's why before

you give any blood you need to screen it

make sure that it's healthy and clean

and does not contain hiv hepatitis b

hepatitis c and others back to hemolysis

what are the complications of hemolysis

remember that this is a red blood cell

right red blood cell so like any cell it

has lots of potassium because potassium

is more abundant intracellularly than

extracellularly it has phosphate

remember atp

and the membrane has what

phospholipid okay and hemoglobin that's

in the red blood cell so when the red

blood cell bursts it will release tons

of potassium and phosphate and

hemoglobin into the blood causing

hyperkalemia hyperphosphatemia

phosphate and calcium like hate each

other there is an inverse relationship

between them we call this the solubility

product so whenever phosphate goes up

usually calcium goes down hemoglobin

lots of hemoglobin in the blood is

called hemoglobin anemia eventually it's

going to end up in the kidney hemoglobin

area hemoglobin can destroy your kidney

kidney failure and hemosiderin auria

cetera means iron as you know hemoglobin

is made of heme and globin and the heme

is made of iron and protoporphyrin these

two doofuses are toxic to the kidney if

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