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Dr. Ashay H. Nandeshwar
M. D., (Ayu)(Mumbai)
(Podar Govt. Medical College)
P.G.D.M.L.T., L.Lb. (Sch)
Lecturer V.P.A.M.C.
Sangli |
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| Definition:- |
Resistance of the body against the pathogenic agents is known as ‘Immunity’.
It is the ability of the body to resist different types o foreign bodies like bacteria, virus, and toxic substances etc. which enter the body.
Types:-2 types – a) innate immunity
b) acquired immunity
a) Innate Immunity:-
It is also called a Natural immunity. It is present from birth and it is the inborn capacity of the body to resist the entry of microorganisms into the body.
It includes –
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Phagocytosis of bacteria and other invaders by WBCs.
Cells of tissue microphages system.
Resistances of skin.
Presence of certain chemical compounds that lysozyme, basic polypeptide, natural killer lymphocyte.
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b) Acquired Immunity:-
It is called as Adoptive Immunity also. Acquired immunity is the resistance developed in the body against any specific foreign body like bacteria, viruses, toxins, vaccines or transplanted tissues. So it is also called as ‘Specific immunity’.
Types of Acquired immunity –
a) Active immunity
b) Passive immunity
Acquired immunity developed by entrance of any foreign, foreign body or a vaccine is called ‘Active immunity’.
Acquired immunity developed by transferring antibodies, Serum or lymphocyte from an immune individual is called ‘Passive Immunity’.
Types of Aquired Immunity –
a) Cellular immunity
b)Humoral immunity |
| a) Cellular immunity – |
| Cellular immunity is by activation of T-lymphocytes which destroy their organisms, entering the body. This is also called as ‘Cell Mediated immunity or T-cell immunity’. |
| b)Humoral immunity – |
Humoral immunity is by the activation of B-lymphocytes. This is also called ‘B-cell immunity’.
Lymphocytes Are Responsible for Acquired Immunity –
A) Development of lymphocytes – In fetus, lymphocytes develop from bone marrow.
The pluripotent hemopoietic stem cells give rise to colony forming units (CFU) and lymphoid stem cells (LSC).
LSC give rise to
Lymphoblasts
Lymphocytes
B) Location of lymphocytes – most extensively located in lymph in lymph nodes, but they are also found in special lymphoid tissues such as spleen, submucosal areas of gastrointestinal tract, thymus and bone marrow.
Humaral immunity
T lymphocyte – thymic & B-lymphocyte – Bursal
C) Formation of antibodies and sensitized lymphocytes by a lymph nodes in response to antigens
D) Thymus gland Pre processes the T-lymphocytes – |
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After origination of T-lymphocytes in the bone marrow 1st migrate to the thymus gland.
They divide rapidly and at the same time develop extreme diversity for reacting against different specific antigens.
One T-lymphocyte develops specific reactivity against one antigen then the next T-lymphocyte develops specificity against another antigen.
This continues until there are thousands of different of different types of T-lymphocytes with specific reactivies against many thousands of different antigens.
Different types of T-lymphocytes now leave the thymus and spread by blood throughout the body to lodge in lymphoid tissue everywhere. |
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| D) Liver and Bone Marrow Preprocess the B-lymphocyte – |
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In human being, B-lymphocytes are known to be preprocessed in the liver during midfetal life and in the bone marrow during late fetal life and after birth.
B-lymphocytes are different from T-lymphocytes in 2 ways – one is – instead of the whole cell developing reactivity against the antigen, as occurs for the T-lymphocytes, the B-lymphocytes actively secrete antibodies that are reactive agents.
Second is – B-lymphocytes haven been greater diversity than the T-lymphocytes, thus forming many millions of types of B-lymphocytes antibodies with different specific reactivities. |
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