ImmunologyLecture 1

Today's lecture is going to summarize the whole course and there are going to be things that you may not understand. Also, they are going to be some points that are very summarized, because later on you will have a whole lecture on it.

The goal of this lecture is to give an outline of the course immunology .Let's start with the basics:

Our world is full of microbes, we eat them, we drink them, we touch them, and we breathe them in whether we like it

or not .They are available everywhere, But we don't fall ill everyday because of the blessing of Allah (SWT) and thanks to our immune system.

Immunity: this word comes from the Latin word immunitus which means "freedom from"

And in this case it means freedom from disease, and freedom from infection.

So, although our world is full of microbes we do not fall ill because of the blessing of our immune system.

Components of the Immune system : These components are of academic interest because they help us to explain and understand more about immunology.

1 .Adaptive and Innate Immunity

2 .Cells of the immune system3 .Soluble mediators of the immune system

4 .Antigens5 .Vaccinations

6 .ImmunoPathology

Let us start with the first one: Adaptive and Innate immunity:

Why do we need different types of immunity?

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Because, there are millions and millions of microbes and millions of types of bugs.

I want you to think of immunology as a state of war between your body and microbes.

And in any war you have a first line of defense, and a second line of defense. This is how we have been created, and that is why we need 2 types of immune responsesWhat is the meaning of immune response?

رد الفعل المناعي To have a reaction you first have to know the microbes

and then know how to deal with it .

The immune response has 2 parts :Recognition and Reaction (elimination) So, first it recognizes the invader and then gets rid of it.

So, the immune response is either innate (non-adaptive) and adaptive (acquired)What are the basic differences between adaptive and innate immune responses?

There are so many difference however there are three 3 vital differences between adaptive and innate immunity. When you see the microbe for the first time, you will form antibody response to this microbe; this antibody response will protect you in the future against this microbe only.

If you take a vaccine for measles, this will produce antibodies and protect you against measles only. It will not protect you from HIV. This type of immune response is

adaptive, it is acquired .So, the adaptive immune response is specific. The innate immune response is NOT specificLet's take an example for innate immune response:

Your innate immune system will not allow measles and prevent HIV. It does not differentiate between the two (Treats them the same way)

The first main difference between the innate and adaptive immunity is the specificity. (Meaning in adaptive immunity

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this immune response is specific for this microbe only, while innate is not specific)

2nd when I give you a vaccination for measles, a memory is created also known as immunological memory. This memory will help you remember this particular bug, this particular measles if you meet this measles again you will eliminate it faster and quicker, and eliminate it before it causes disease.

This memory is a characteristic of the adaptive (acquired) immune response NOT the innate immunity .

The innate immune response will not remember if it met measles or not, but the adaptive immune response will .

So the first major difference is specificity, the second difference is memory. And the last major difference is self recognition.

Self recognition: I have my own kidney and you have your own kidney. I do not respond to my kidney and you do not respond to your kidney by forming an antibody

If I take your kidney and transplant it into my body and if it is not compatible then I will form antibodies against this kidney.

It is the same kidney that was living happily ever after in its original location.

So you have these organs full of antigens but you recognize them as self and do not respond to them because you do not form an immune response to self.

But if you take a kidney and put it in somebody else and this person is not compatible. The new person will form an

immune response .This is called self discrimination. You discriminate between your self and everything else.

Your antigens are self and anything else is not, even your fathers or your mothers antigens are not. Anything else in not self.

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- What are the three criteria for adaptive immune response ?

If it is specific, it has memory and it is involved in immune response and self discrimination.

Innate immunity is not specific and has no memory and doesn't have (little or no involvement) with self discrimination.

So, why do we need these 2 types of immune responses?We need them because there are different microbes and we need the first line of defense and we need the second line of defense.

The fact is that innate immune response is not specific and doesn't have any memory and no sense of discrimination this doesn't decrease the value of innate immune response.

We will know in the future that these are very important components of the innate immune system .

)Very important slide (

Cells of the immune system : They are the officers; the soldiers and the workers. They are the machines that do the work. So, the response to a pathogen is done by cells of the immune system.

There are 3 different categories of the cells of the immune system. The lymphocytes, the phagocytes and the secondary auxillary cells (secondary)

These are the cells of the immune system .Diagram is very important.

Lymphocytes are B cells, T cells and LGL (Large Granular Lymphocytes such as NK CellNK=Natural killer.

Phagocytes are different and the auxillary cells are different.

Do not imagine that the phagocytes are in one room, and the B cells in another room and the T cells in another, and that each is working alone

NO! they interact with each other and they work with each other. They communicate together and they are a part of one system

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Ultimately THEIR GOAL is the same.And ultimately there is interaction is in the form of communication. It is either direct communication (touch) or by signalsWe will talk about these cells in details in the next lecture.

So we are just going to touch on this very lightlyWe said that the lymphocytes re very important cells for acquired immune response. They identify microbes specifically.Lymphocytes are B cells and T cells and natural killer cells.

B cells : The B cells are born in the bone marrow and they mature

and develop in the bone marrow and they mature to form Plasma cells.

Plasma cell function= secretion of antibodies

All the B cells are programmed to identify a specific part of one antigen.

We make millions and millions of antigens and each B cell is responsible for knowing one antigen and inside the antigen there is a specific area for the antigen. So each cell is programmed to recognize one antigen (one part of the antigen)

So, the ultimate goal is to increase the number and they become plasma cells and the function of the plasma cells is to secrete antibodies.

These antibodies have a function of killing the pathogen that lives OUTSIDE the cells.

Some of these pathogens are inside the cells and some of them live outside the cell. And the function of the antibodies is to fight the pathogens that live OUTSIDE the cell.

This is the story : One B cell will recognize one part of one antigen (This is

called Recognition) and after this recognition there is selection and after that there is increase in number (this is Proliferation).After that, we have maturation to form plasma cells.

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What is the function of the plasma cell? They secrete antibodies.What do the antibodies do? They work on the microbes.

There is one type of cell that we did not talk about as yet. It is the memory cell .What is its function ?

Memory cells function is memory this will remember the microbe and if this microbe enters the body again then the reaction will be faster and stronger. This is because of the memory response

Wishing you all a wonderful 3rd yearI hope this Helps….And please remember me in your

du3aas

T cells : There are 2 types: Either T-Helper or T-cytotoxic

They come from the bone marrow and they leave the bone marrow very early (when they are immature) and then they go to the thymus and mature there (like they go to the nursery and then the school and then the university and then they graduate from there to become T-effector cells).

So, when they leave the Bone marrow they are NOT T-cells they are immature T-cells /Future T-cells (mashroo3 T-cells)

A. T-helper Cells:

They are either T-helper cells (help all the cells of the immune system to do their jobs better: for E.g. it helps the B-cells, phagocytes, and it helps T-cytotoxic)

B. T-cytotoxic cells: (Cyto= cells, toxic=Killing: cytotoxic=killing cells)

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They kill the cells that have been infected with viruses or with an intracellular pathogen or cells that are tumor cells(

NOTE:There are many types of T-cells BUT T-EFFECTOR cells include T-cytotoxic & T-helper cells ONLY .

So, B cells deal with extra cellular antigens while T-cytotoxic cells deal with intracellular antigens.For example: Tuberculosis and some type of tumors

-T-Helper cells get divide into 2 types and later on we will know them .

-We know that T-cytotoxic cells kill cells that are infected with viruses and this is a common role between it and the N.K cells…Laish Al ta'9arub hatha?

There are 2 different types of cells and they do the same jobBUT, The T-cytotoxic tab3 al adaptive immunity and adaptive immunity will be acquired so it takes 2-3 days.

So, you are not left open (defenseless) for 2-3 days. You have been created with another set of weapons which are ready now. Which are the N.K cells.

Roughly they do the same job as the T-cytotoxic cells but these are part of the innate immune response .

The NK cells do the work until the T-CYTOTOXIC TAKE OVER

N.K CELLS: They are large granular lymphocytes and they destroy tumor cells and viral infected cells(like the T-

cytotoxic cells)

Phagocytes : From their name it is very clear for us to know what they

do .Phagocytosis:

They recognize the bacteria and then they engulf the bacteria and destroy it.

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The professional phagocytes are Monocytes, macrophages and neutrophils.

There are other cells that have phagocytic functions, But these are the three main types of phagocytes

Monocytes, macrophages: these live for a long timeNeutrophils: these live for a short timeMonocytes and macrophages they are found in the circulation for a long tome and when they leave the circulation and go to the tissue they are known as tissue macrohphages.

Tissue macrophages are found in many places. Almost any tissue in your body will have resident macrophages.

What are the resident macrophages of the liver: kuppfer cellsAlso we have the mesenangial cells, Langerhanz cells all these and macrophages present in different locations

Phagocytosis is very simple: recognition, internalizations, and destruction.

2ndry cells have 2 nd ry jobs ------------------------------------------------

We have spoken about innate and acquired immunity and also about the cells of the immune systemAnd we divided them into Lymphocytes, phagocytes and other cells such as auxiliary cells.

And the lymphocytes we divided them into B-cells T-cells(T-helper and T-cytotoxic)And then we spoke about the Phagocytes (macrophages and neutrophils.

Now we will talk about

Soluble mediators of the immune response : Soluble means they are soluble in blood and they are present in the secretions of your body. And they help defend your body against the microbes. Sometimes they are called humoral

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They are: Antibodies, Cytokines, Complement, and acute phase protein .

What are antibodies?Antibodies come from a stage of the B cells called plasma cells and they all have the same basic structure.

Antibodies have a common structureThis part is called is called F(ab) and this part is called F(c)(On the drawing):

F(ab) is the part that is used to recognize the antigen.And The F (c) part binds to the cell.This is the structure of the antibody.See slides to understand this:

In this you will see that there is binding, but in the other there is no binding, WHY?

Because of the SHAPE, The chemical shape of the antibody has to be compatible with the chemical shape of the antigen for it to work.

This antibody recognizes That antigen. So it binds to the complement and then to the cells(All cells such as F(ab) and N.K cells).

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Cytokines : When you hear the word cytokines, remember the word

messages.Cells are deaf and blind, but they need to communicate and speak to each other, so that they can work in harmony for whatever job they are doing and one method of communication is by using cytokines.

Cytokines are small molecules and they serve as signal molecules between one cell and another.

They are proteins, peptides, glycoproteins.

An example for cytokines is interferons. InshaAllah we will talk about this later

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These cytokines are Messenger molecules between one cell and another cell.Example:

Interferons: are anti-viral cytokines. They help prevent the infection of the cells by the virus. So, they are secreted by some cells to protect other cells from viral infection.

ComplementWe have a whole lecture on this. The complement system

is 20 serum proteins; it is either activated directly or indirectly.The direct activation is by the alternative

pathway. The binding of the antibody to the microbe will activate the classical pathway.

Once it is activated, Some people say complement= lysis.NO, Complement= lysis + opsonization< This is the correct statement.What is opsonization ?

If you have food without salt, without pepper and without spices and you are hungry, then you will eat it.

This is called phagocytosis. But if you add salt and pepper you will eat this food better and this is known as Opsonization:Enhancement of phagocytosis due to antibody and complement this is called opsonization, So opsonization is enhanced phagocytosis.

So we said that complements preform phagocytosis and opsonization and they also do chemotaxis.What is Chemotaxis?

Attraction of cells to the site of inflammation

Again,Antingens are recognized by the b-cell and the t-cells.

We said that the Antibody recognizes antigen by the shapeIf the shape fits then there will be binding, if it doesn't fit

then there will be no binding .

The story is different for T-cells

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It doesn't bind with the antigen directly. It needs a helper who, Chops, and prepares and cook it for a while and give it to the T-cell.Otherwise it will not touch it.

This helper is called APC APC: Antigen presenting cellThis is a cell that presents the Antigen to the T cells.

When the antigen enters the body, the B cell doesn't have a problem, it recognizes it directly from the shape.With the T-cell the story is different

The antigen has to be chopped and put on a plate and presented to the T-cell. Then the T-cell will recognize itThis is the story of antigen recognition by B-cell and By T-cell.The APC will present the antigen to the Cells.

Finally, the antigen is the foundation of immunology. If there is no antigen there is no need for immune response.

So for the B-cell the shape of the antibody has to be compatible with the shape of the antigen. But with the T-cells the story is different; you have the APC which presents it to the T cells.

After the antigen is recognized, it is eliminated (Destroyed) by 3 methodsneutralization, phagocytosis and cytotoxicity

The last 2 components we will cover very quickly because we have destoyed them already

Vaccination : When we take the kid to the clinic and give him a dose of vaccination. The reason behind this dose is to expose the child to the antigen. So that he has an immune response against the antigen and in the end he will have memory cells.

So, if this child is infected by measles. It will be quickly destroyed. And this is the basics of vaccination

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So, vaccination is based on primary immune response which results in memory.

So next time there is an infection the immune response will be very fast and huge and this will cause the elimination of the microbe before it causes any harm

You have heard the good news about the immune system. But the immune system is a weapon with 2 sides to it.

The immune system and the immune response have to be carefully controlled.

This is a weapon and it needs to be carefully controlled otherwise immune response will result

If you have too much immune response then this is called hyper sensitivity .

For example, eczema, allergy, asthmaThis is over reaction, hyper reaction, Too much immune response to small things.So the immune response has to be controlled.

Because if it overworks then this leads to hyper-sensitivity and if it doesn't work then this leads to immuno-deficiency.

Too much immune response: hyper sensitivity.For example: HIV infection resulting in AIDS

Too little immune response: immuno-deficiency.And if you have an immune response against your own antigens this is called Auto immune.

May You have the most active immune system ever,Afrah S. Sait

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