B cell and T cell

The human acquired immune system is responsible for protection of body from different kinds of pathogens as well as foreign particles that enters the body, When any foreign particles are pathogens that enters in the body, our acquired immune system detect it and learn how to kill it and what type of mechanism is follow for destruction of this pathogenic substance. When they detect specific pathogens then they show response against those pathogens.

PART OF ACQUIRED IMMUNE SYSTEM:

Our acquired immune systems consist of the two basic parts such as:

T cell
Bcell
Both T cell and B cell play a very important role for body defense mechanism.

Activation of acquired immune system:

Acquired immune system is activated when any foreign particle enter the body, these system detect it and then prepare itself for attack. The entire foreign particle that enters the body is detected by the body because these particles have a unique pattern on its surface which is different from body cell.

Antigens:

When our immune system detects pathogens and kills it with the help of specific site that is present on the surface of the cell called antigen.

Receptor:

When the immune system show a response against a pathogen because of site present on the cell called receptor site. Our immune system consist of different kind of cell each cell has a unique receptor site therefore protect or defense our body against different kind of pathogens.

Macrophages:

It is the largest white blood cell and helps to speed up the activation of acquired immune system. It is present in our whole body, detect pathogen, and kill them.

Lymphocytes:

Our body consists of R.B.C and lymphocytes.

Lymphocytes' consist of five different kind of white blood cell that is circulating in the body. But the most important present in the lymphocytes is T cell and Bcell.

T cell:

v Origin of T cell: T cell is originating from bone marrow but they are mature in the thymus gland and this gland is present in the chest cavity.

v Position: T cell is present interior of lymph node.

v Tissue distribution: T cell is distributed in the porafolicular area of cortex and poriarterol of the spleen.

v Life span: The life span of T cell is long as compared to B cell

v Surface antibodies: t cell lack of surface antibodies.

v Lymphokines: They secrete large amount of lymphokriens

v Percentage of T cell: The lymphocyte contain about 80? of T cell.

Types of T cell:

T cell is of three types such as:

1. Helper T cell

2. Cytotoxic T cell

3. Suppressor T cell

Helper T cell:

It is the most common type of T cell. It provide defense to a body as well as help to regulate the immune function of the body. Helper T cells secrete a specific kind of chemical called lymphokines which activate other T cell and help them to grow.

Cytotoxic T cell:

These cells are very important because it provide a specific defense against pathogens. They inhibit the production of abnormal or tumor cell in the body. These are very important because of production of specific a protein called perforin, these proteins form a small hole in the cell membrane of pathogens which may be virus or bacteria and destroy their structure. These proteins are directly fall on the target cell and cannot harm to the surrounding cell.

Suppressor T cell:

These are so called suppressor because it suppress the activity of other T cell such as cytotoxic and helper cell. It help in regulation of immune system as well as inhibit the destruction of body own tissue such as autoimmune disease.

Production of T cell:

It is produce in the stem of bone marrow and matures in the thymus from there this cell stay for three week in thymus. Here the T cell is mature and purpose of maturing T cell in the thymus is to get different types of receptor, which is used to determine the different kind of foreign particle.

Activation of T cell:

T cell are activated by B cell and detect the pathogen with the help of antigen presenting cell that eat foreign substance such as bacteria, protists ,virus etc, these cell breakdown into small pieces. When the response of T cell is activated a lot of T cell release in the blood which cause destruction of pathogens.

Function of T cell:

v T cell form cell mediated immune system

v T cell provide protection against various pathogens

v It helps activation ofmacrophages and eosinophills

B cell:

v Origin: It was first introduce by "busra" of "fabricius" which the organ of bird but this organ is not present in human therefore it is produce in bone marrow.

v Receptor:

v B cell having a speficic binding receptor for antigen which helps to bind to different kind of toxic substance.

v Position:

v It is present on outside of lymph node

v Life span: life span of B cell is very short.

v Secretion: B cell secretes an antibody which provides immunity to the body.

v Percentage of B cell: It from about 20% of lymphocyte.

Production of B cell:

B cell is produce in bone marrow where they mature. Here these cells receive a specific receptor and release in the blood from there B cell enters into lymphatic tissue. B cell having a protein called immunoglobin protein which are placed together in different combination on, the surface of B cell and help in detection of pathogen.

B cell activation:

Activation of B cell take place in the lymph node, when foreign agent enter the lymph node, its stimulate B cell. The receptor of B cell binds to the foreign particle and starts to multiply and increase its number. When B cell activate then they enter the blood and change into plasma cell.

Types of B cell:

B cell is of two types such as:

1. Plasma cell

2. Memory Bcell

Plasma cell:

These are the type of B cell which helps in production of only single kind of antibodies. These antibodies are release in the blood and protected the body from different disease caused by different pathogen. The body is immune still the antibodies release in the blood.

Memory B cell:

After detection of pathogen and its destruction the cell that is produced by B cell is called memory B cell. These cell move to lymph node and show a quick response against a pathogen that again enter the body and prevent the again attack of pathogen. Because these cells know the mechanism of killing the pathogen that already entered and causes a disease in the body.

Antibodies:

It is the protein which is produce by B cell; these antibodies bind to antigen and kill them.

Antibodies have many uses such as:

Ø It target the organism that cause the infection

Ø Remove the toxin from the body

Ø It remove the foreign antigen that circulate in the blood

Ø It helps to activate the complement system

Ø It helps to activate the mast cell

Structure of antibodies:

Antibodies are immune system related protein called immunoglobin protein. Each immunoglobin has four polypeptide chains that are two heavy chains and two light chains which are joined in such a way to form y shaped molecule, the amino acid sequence among the tip of antibodies different in different antibodies.

Antibodies as two regions such as constant and variable regions.

Variable region: These regions are composed of 110-130 amino acids and this region provides specificity for binding a specific antigen. It includes the end of light and heavy chains.

Constant region: These regions determine how antigen is killed and what type of mechanism is used.

Antibodies are divided into five major classes such as:

1. IgM

2. IgG

3. IgA

4. IgD

5. IgE

All of above immunoglobin are based on constant region of antibodies and immune function.

Whole mechanism of T and B cell:

Structure of antibody