Understanding the Cells of the Immune System

Summary

In this video, Tom from Zero to Finals explains the different cells involved in the immune system, focusing on their development, differentiation, and interactions. The video covers the roles of myeloid and lymphoid stem cells in creating various immune cells like macrophages, neutrophils, T cells, B cells, and natural killer cells. It also highlights the importance of dendritic cells in initiating specific immune responses. The overview aims to provide a foundational understanding for later, more detailed videos on immune cell interactions.

Takeaways

• 🛡️ Immune cells are crucial for defending the body against pathogens and destroying abnormal cells like virally infected or cancerous cells.
• 🌱 The development of immune cells begins in the bone marrow with pluripotent hematopoietic stem cells, which have the potential to become various blood cell types.
• 🔬 Myeloid stem cells differentiate into immune cells, platelets, and red blood cells, playing a key role in the innate immune system.
• 🩸 Megakaryocytes are large cells that produce platelets essential for blood clotting.
• 🔴 Reticulocytes are immature red blood cells that lose their nucleus and eventually become mature red blood cells carrying oxygen throughout the body.
• 👨‍🔬 Myeloblasts can differentiate into various immune cells, including monocytes, which mature into macrophages, and neutrophils, which are the first responders to pathogens.
• 🔴 Eosinophils contain granules with toxic chemicals for large pathogens and are involved in parasitic infections.
• 🌀 Mast cells and basophils contain granules with cytokines that can be released in response to pathogens, contributing to the immune response.
• 🔬 B lymphocytes or B cells mature in the bone marrow and produce antibodies specific to antigens on pathogens.
• 🔬 T lymphocytes or T cells mature in the thymus and have T-cell receptors for specific antigens, with subsets including CD4 (T helper cells) and CD8 (cytotoxic T cells).
• 🛑 Natural killer cells are activated by cytokines and can kill infected or abnormal cells without requiring specific antigen recognition.
• 📬 Dendritic cells are antigen-presenting cells that capture, process, and present antigens to T cells, initiating the specific immune response.

Q & A

What is the primary function of immune cells?

The primary function of immune cells is to defend the body against pathogens and destroy abnormal cells such as virally infected cells or cancer cells.

Where does the development of immune cells begin?

The development of immune cells begins in the bone marrow with a pluripotent hematopoietic stem cell.

What is the difference between myeloid stem cells and lymphoid stem cells?

Myeloid stem cells differentiate into various types of immune cells, red blood cells, and platelets, while lymphoid stem cells differentiate into lymphocytes, which are part of the specific immune system.

What is the role of megakaryocytes in the immune system?

Megakaryocytes are responsible for producing platelets, which are essential for forming blood clots.

How do reticulocytes differ from mature red blood cells?

Reticulocytes are immature red blood cells that have lost their nucleus but still contain remnant RNA material called reticulum, which gives them a net-like appearance under a microscope.

What is the function of macrophages in the immune response?

Macrophages are part of the innate immune system and serve as the first line of defense against pathogens. They recognize and destroy pathogens or abnormal cells through phagocytosis and secrete cytokines to initiate an inflammatory response.

How do neutrophils contribute to the innate immune system?

Neutrophils are attracted to pathogens and destroy them through phagocytosis. They are a general attack cell in the innate immune system and respond to signals from macrophages to migrate to areas of inflammation.

What is the purpose of eosinophils in the immune system?

Eosinophils are important in dealing with large pathogens that cannot undergo phagocytosis, such as in parasitic infections. They contain granules with pro-inflammatory cytokines and toxic chemicals that can damage or kill pathogens.

How do B lymphocytes or B cells participate in the specific immune response?

B cells have antibodies on their surface that match specific antigens on pathogens. Upon activation by the specific antigen, B cells multiply and differentiate into plasma cells, which produce antibodies, and memory B cells, which provide a rapid response upon re-encountering the same pathogen.

What is the distinction between CD4+ T cells and CD8+ T cells?

CD4+ T cells, also known as T helper cells, provide signals to activate other immune cells, including CD8+ cells. CD8+ T cells, when activated, differentiate into cytotoxic T cells, which can destroy infected or abnormal cells.

What is the role of dendritic cells in the immune system?

Dendritic cells are responsible for taking up antigens in infected tissue, processing them, and presenting them on their cell membrane to CD4+ and CD8+ T cells, initiating the specific immune response.

How do natural killer cells differ from other cells of the specific immune system?

Natural killer cells are activated by cytokines and interferons and can recognize and kill infected or abnormal cells without requiring specific antigen receptors or MHC molecules.

Outlines

00:00

🛡️ Immune System Cells Overview

This paragraph introduces the immune system's cellular components, emphasizing their role in defending the body against pathogens and abnormal cells. It explains the development of immune cells in the bone marrow, starting from pluripotent hematopoietic stem cells. These stem cells differentiate into various types, including myeloid stem cells and lymphoid stem cells. Myeloid stem cells give rise to cells like megakaryocytes, which produce platelets, and reticulocytes, immature red blood cells. The paragraph also covers the differentiation of myeloblasts into monocytes, macrophages, neutrophils, eosinophils, mast cells, and basophils, which are integral to the innate immune system.

05:01

🔬 Innate and Adaptive Immune Cells

The second paragraph delves into the specifics of the innate immune system, detailing the functions of cells like macrophages and neutrophils in pathogen destruction through phagocytosis. It also discusses the roles of eosinophils in parasitic infections and the release of toxic chemicals from mast cells and basophils. The paragraph transitions into the adaptive immune system, highlighting the lymphoid stem cells that differentiate into B lymphocytes, T lymphocytes, and natural killer cells. B cells are characterized by their surface antibodies specific to antigens, leading to the production of plasma cells and memory B cells upon activation. T cells are further divided into CD4+ T helper cells and CD8+ cytotoxic T cells, which are crucial for the adaptive immune response.

10:03

🌐 T Cell Maturation and Function

This paragraph focuses on the maturation of T cells in the thymus gland and their differentiation into various types based on the receptors they display. CD4+ T cells become T helper cells, which are essential for activating other immune cells, including CD8+ cytotoxic T cells. These cytotoxic T cells can destroy infected cells through cell lysis or the Fas pathway. The paragraph also introduces natural killer cells, which can recognize and kill infected or abnormal cells without the need for specific antigen receptors. Additionally, it discusses the role of dendritic cells in antigen presentation to both CD4 and CD8 T cells, initiating the specific immune response.

15:04

📚 Resources for Medical Students

The final paragraph serves as a call to action for viewers, encouraging them to like, comment, and subscribe for more educational content. It also directs viewers to the Zero to Finals website, which offers notes, illustrations, practice questions, and a blog designed to assist medical students in preparing for exams and their future careers as doctors. The speaker expresses hope that the video was helpful and invites viewers to explore the series for comprehensive knowledge on the immune system.

Keywords

💡Immune System

The immune system is a complex network of cells, tissues, and organs that work together to defend the body against harmful pathogens such as viruses, bacteria, and other foreign invaders. In the video, the immune system is the central theme, as it discusses the various cells involved in defending the body and destroying abnormal cells like virally infected or cancer cells.

💡Pluripotent Hematopoietic Stem Cell

A pluripotent hematopoietic stem cell is an undifferentiated cell found in the bone marrow that has the potential to develop into various types of blood cells. The video explains that these stem cells are the starting point for the development of immune cells and can be stimulated to specialize into different types, such as myeloid or lymphoid stem cells.

💡Myeloid Stem Cell

Myeloid stem cells are a type of stem cell that gives rise to various immune cells, as well as red blood cells and platelets. The video describes how these cells can differentiate into megakaryocytes, which produce platelets, and reticulocytes, which mature into red blood cells. They also can become immune cells like monocytes, neutrophils, and eosinophils.

💡Lymphoid Stem Cell

Lymphoid stem cells are responsible for the development of lymphocytes, which are a type of white blood cell crucial for the adaptive immune response. The video explains that lymphoid stem cells can differentiate into B lymphocytes, T lymphocytes, and natural killer cells, each playing a distinct role in the immune response.

💡Macrophages

Macrophages are large immune cells that play a critical role in the innate immune system by engulfing and destroying pathogens through a process called phagocytosis. The video describes macrophages as the first line of defense for pathogens that have penetrated the body's barrier defenses and their role in initiating the inflammatory response by secreting cytokines.

💡Neutrophils

Neutrophils are a type of white blood cell that are attracted to and destroy pathogens as part of the innate immune system. The video mentions that neutrophils circulate through the bloodstream and migrate to areas of inflammation, where they perform phagocytosis to eliminate pathogens.

💡B Lymphocytes (B Cells)

B lymphocytes, or B cells, are a type of lymphocyte that mature in the bone marrow and produce antibodies specific to antigens displayed on pathogens. The video explains that when B cells encounter their specific antigen, they multiply and differentiate into plasma cells, which produce antibodies, and memory B cells, which provide long-term immunity.

💡T Lymphocytes (T Cells)

T lymphocytes, or T cells, are another type of lymphocyte that mature in the thymus gland. The video describes T cells as having T-cell receptors that recognize specific antigens, and they differentiate into various types, such as CD4+ T helper cells and CD8+ cytotoxic T cells, which are crucial for the adaptive immune response.

💡Cytotoxic T Cells

Cytotoxic T cells are a subset of T cells that are capable of killing infected or abnormal cells. The video explains that these cells become activated when their T-cell receptors match a pathogen, and they can destroy target cells through cell lysis or by activating the apoptotic pathway in the target cell.

💡Natural Killer Cells

Natural killer cells are part of the innate immune system and are capable of recognizing and killing infected or abnormal cells without the need for specific antigen recognition. The video describes how these cells are activated by cytokines and interferons and can induce cell death through apoptosis.

💡Dendritic Cells

Dendritic cells are antigen-presenting cells that play a crucial role in initiating the adaptive immune response. The video explains that dendritic cells take up, process, and present antigens to T cells in the lymphoid tissue, such as lymph nodes and spleen, acting as messengers that alert the immune system to the presence of a specific pathogen.

Highlights

Introduction to the immune system and its role in defending the body against pathogens and abnormal cells.

Overview of the development of immune cells from pluripotent hematopoietic stem cells in the bone marrow.

Explanation of the differentiation of hematopoietic stem cells into myeloid and lymphoid stem cells.

Description of myeloid stem cells and their role in producing platelets and red blood cells.

Details on megakaryocytes, their structure, and their role in producing platelets.

Explanation of reticulocytes, their immature state, and transformation into mature red blood cells.

Role of hemoglobin in red blood cells and its importance in oxygen transport.

Function of monocytes and their differentiation into macrophages.

Explanation of macrophages, their role in phagocytosis, and their importance in the innate immune response.

Introduction to neutrophils and their function as general attack cells in the innate immune system.

Role of eosinophils in responding to large pathogens and their method of degranulation.

Description of mast cells and basophils, their similarities, and their role in the immune response.

Overview of the lymphoid stem cell and its differentiation into B cells, T cells, and natural killer cells.

Function of B lymphocytes, their antibodies, and their role in the specific immune response.

Explanation of T lymphocytes, their maturation in the thymus, and the role of T helper cells and cytotoxic T cells.

Introduction to natural killer cells and their function in recognizing and destroying infected or abnormal cells.

Role of dendritic cells in antigen presentation and initiating the specific immune response.

Summary of the overview of immune system cells and their importance in medical education and practice.

Transcripts

hi this is tom from zelda finance calm

this video is designed to cover the

different cells involved in the immune

system so these are the cells

responsible for body's defenses to

pathogens and are responsible for

destroying abnormal cells such as

virally infected cells or cancer cells

specifically we're going to look at the

family tree of these cells of this

importance understand where these cells

come from how they develop and

differentiate and how they relate to

each other this will give you a good

overview and reference point for later

videos where we'll go into detail about

how these cells interact to provide an

immune response

so the development of immune cells

happens in the bone marrow and it starts

with a pluripotent hematopoietic stem

cell so Clarie meaning multiple potent

meaning potential he motto meaning

relating to blood and poetic meaning

creative and then stem cell being an

undifferentiated cell that has the

potential to create multiple different

types of blood cell

so when this cell is stimulated by

chemicals called differentiation

inducers it starts to specialize in to a

variety of different types the first

subdivision is to become either a

myeloid stem cell or a lymphoid stem

cell now myeloid refers to the bone

marrow and lympho refers to the

lymphatic system

so first let's look at myeloid stem

cells as well as the cells of the immune

system myeloid stem cells are also

responsible for producing platelets and

red blood cells so they can become

something called megakaryocytes and mega

means obviously large and carrier refers

to the fact that it has a nucleus and

site meaning cell so as you might

imagine this is a large cell with a big

lobulated nucleus and it's responsible

for producing platelets and platelets

obviously essential for forming blood

clots

so the myeloid stem cell can also become

reticulocytes reticular means net like

and sight means cell so these are

immature red blood cells and they've

lost their nucleus but they still

contain remnant RNA material called

reticulum and this RNA material as you

can see in the picture is sort of net

like

so these reticulocytes are released from

the bone marrow into the bloodstream

where they gradually lose their

reticulum and change shape becoming the

classical donut like red blood cells the

red blood cells themselves can survive

up to three months in the blood and they

contain a lot of a protein called

hemoglobin which is the molecule that

binds to oxygen and allows the red blood

cell to carry oxygen around the body

so normally about 1% of the red blood

cells or reticulocytes and where you see

a larger proportion of reticulocytes to

red blood cells you know that the bone

marrow is having a rapid turnover of red

blood cells and that'll be because of

situations like acute blood loss or

hemolysis where the red blood cells are

being broken down and this causes an

increased rate of production and

therefore a higher proportion of

reticulocytes to red blood cells

so alternatively myeloid stem cells can

become milah blasts and the maiale

refers to the bone marrow and blast

refers to immature cells so these

myeloblast themselves then differentiate

into other immune cells

so they can differentiate into monocytes

and these monocytes then become

macrophages so mono refers to the single

nucleus sight refers to cell macro

refers to the fact that it's large and

phage means to eat so monocytes

circulate through the bloodstream and

then when they enter the tissues they

actually differentiate into the

macrophages so these are very similar

the same family of cell

macrophages can be found in most tissues

in the body and they simply wait in

those tissues to encounter a pathogen

they're the first line of defense for a

pathogen that has penetrated through the

barrier defenses of the body now they

have receptors called toll-like

receptors and these are essential in

recognizing molecules that are unique to

pathogens and these molecules are known

as pathogen associated molecular

patterns or PA MPs

once they recognize a pathogen or

abnormal cell they can then destroy them

using a process called phagocytosis

where they essentially absorb or eat the

pathogen and then digest it from the

inside

they're also essential and secreting

cytokines that initiate the inflammatory

response when these cytokines and

inflammation alert the rest of the

immune system of the infection and then

they generate the immune response

so they're the first step in the innate

immune system it's a response to a new

pathogen and they alert everybody else

so myeloblast can also become

neutrophils neutro refers to neutral and

fill meaning attraction and this

therefore refers to the fact that

neutrophils are generally attracted to

pathogens which described their role as

a general attack cell in the innate

immune system they spend their time

circulating through the bloodstream and

then they migrate to areas of

inflammation in response to signals from

macrophages and there they destroy the

pathogens and abnormal cells again by

phagocytosis

my Oblast can also become something

called a sinner Phil's a sinner refers

to red-colored referring to the fact

that their cytoplasmic granules take up

dyes really well and give a red color

under a microscope the sinner Phil's are

particularly important when the invading

pathogens are too large to undergo

phagocytosis such as in parasitic

infections so they normally hang around

in tissues until they're activated by

cytokines or they respond to an invading

pathogen

so they have granules that contain

pro-inflammatory cytokines and chemicals

that are directly toxic to pathogens and

parasites such as major basic protein

which is an enzyme that digests

parasites these chemicals can be

released in a process known as

degranulation or exocytosis in which the

granules fuse with the cell membrane and

then they're released into the

surrounding space where they can travel

to cause damage to nearby pathogens

these cinder fills are also capable of

phagocytosis but not usually to the

extent of macrophages or neutrophils

so the myeloblasts can also become

Marcel's and basophils and these are two

very similar types of cell that both

contain cytoplasmic granules that have

various cytokines in them and they can

be released in response to a pathogen

again by degranulation

the main difference between these two is

that Marcel's are fixed in place in the

tissues whereas basophils circulate

through the blood

and that basically concludes all of the

cells that result from the myeloid stem

cell and these cells are responsible for

is called the innate immune system so

the innate immune system forms the first

line of defense to pathogens within the

body and involves the mechanisms for

general recognition and destruction of

pathogens

so next let's look at the cells of the

specific immune system and these results

from the lymphoid stem cell so the

lymphoid stem cell through a series of

intermediate steps including

lymphoblasts can become one of three

types of lymphocyte the first is the B

lymphocyte or B cells they're called B

lymphocytes because they mature into

this type of lymphocyte within the bone

marrow itself

our b-lymphocytes have antibodies also

called immunoglobulins lining their cell

surface these antibodies are matched to

specific antigens that are displayed on

pathogens so each lymphocyte has a

single specific type of antibody that

matches a single antigen

there are millions of different possible

antibodies and therefore millions of

different specific b-cells

so each b-cell is only capable of

recognizing the specific pathogen that

displays the antigen that matches their

antibody

the role of the B cell is that once it

is activated by the specific antigen it

multiplies furiously and becomes either

plasma cells or memory b-cells

plasma cells produce fast quantities of

antibodies against the pathogen and the

memory b-cells

hang around long after the pathogen has

been cleared so that they can respond

much quicker when they encounter that

pathogen again

the second type of lymphocyte is the T

lymphocytes or T cells and the code T

cells because they actually leave the

bone marrow has PROFIBUS sites and

traveled to the thymus gland where they

mature into T cells

details have t-cell receptors on their

cell surface that are specific in the

same way as antibodies on b-cells to a

specific antigen and so therefore only

the t-cell specific to the invading

pathogen will become active in an

infection

so t-cells fall into two categories

based on the type of receptors that they

display the t-cells that display cd4

receptors are called cd4 cells and the T

cells that display the cd8 receptors are

called cd8 cells and importantly cd4

cells respond to MHC class 2 receptors

on other cells of the body and the cd8

cells respond to MHC class 1 receptors

on other cells and this is important to

remember and will become a lot clearer

over time as we go through some of the

other details of the specific immune

system so cd4 cells become T helper

cells when they're activated many cells

in the immune system rely on these T

helper cells to provide signals that

then activate them including the cd8

cells so with the help of T helper cells

cd8 cells become activated when their T

cell receptors match a pathogen and they

multiply very quickly and differentiate

into cytotoxic T cells

so cytotoxic t-cells can destroy virally

infected or otherwise infected other

cells in two ways the first way is to

attach themselves to the cell and spray

it with proteins that are destructive to

that cell's membrane and therefore

destroy the cell by cell lysis or they

can activate the fast pathway FAS

pathway and this pathway is like a

self-destructive process and it causes

the cell to destroy itself by apoptosis

the third type of lymphocyte is called

natural killer cells

these cells are activated by cytokines

from macrophages and by interferons

and they recognize infected or abnormal

cells like the cells of tumors without

requiring the MHC or specific antigen

receptors

they can then kill these cells by

releasing cytokines that induce cell

death again by apoptosis they can also

secrete something called interferon

gamma that further activates macrophages

so by creating this cycle of macrophages

releasing sides of kinds that then

activate the natural killer cells who

then release the interferon gamma that

further activates macrophages they

create a cycle of positive feedback that

increases the inflammatory response

after contact with a pathogen

so that concludes all the cells that

result from the lymphoid stem cells and

the cells that are involved in the

innate immune system and there's one

final cell type that we need to consider

which is very important within the

immune response and that's dendritic

cells

there are various types of dendritic

cell and they all originate from

different precursor cells however they

perform a very similar function

specialist dendritic cells that are

found in the skin are called Langerhans

cells

so dendritic cells are responsible for

taking up antigens in the infected

tissue processing them and then

presenting the antigens on their cell

membrane for other cells of the specific

immune system to recognize and respond

to they have both MHC class 1 and class

2 molecules on their cell membranes so

they're able to present antigens to both

cd4 and cd8 t-cells they act very much

like postman delivering messages that a

specific type of pathogen has infected a

tissue somewhere else in the body they

pick up these antigens in the infected

tissue travel through the lymphatic

system and the blood to the lymphoid

tissue such as the lymph nodes and

spleen and there they deliver the

antigens to the cd4 and cd8 cells and by

doing this they play an essential role

in initiating the specific immune

response so that summarizes an overview

of the cells of the immune system I hope

you found this video helpful it was

created as part of a set of videos that

covers everything you need to know about

the immune system for medical school and

practicing very well as a doctor so go

ahead and check out the other videos in

this series

if you like this video please like

comment and subscribe for more videos

you can also check out the zero de

Finals web site at zero two finals com

for notes illustrations practice

questions and a blog all of which has

been purposefully designed and built

from the ground up to help you prepare

for your medical exams and for your

future career as a doctor and I'll see

you with the next video