ANTIBODIES – Our Body’s Military Force!


These are the foreign bodies that have the capability to bind with the immunogen and also induce an immune response from our body.
The majority of antigens are made up of protein. But some can also be made of carbohydrates, lipids, or nucleic acid.


An antibody is a protein molecule that is generated in the living being by the plasma membrane of the cell. The majority of antibodies are produced in the blood, hence the name immunoglobulins.
Each antibody consists of four polypeptides– two heavy chains and two light chains joined to form a “Y” shaped molecule.
The amino acid sequence in the tips of the “Y” varies greatly among different antibodies. This variable region, composed of 110-130 amino acids, gives the antibody its specificity for binding antigen.

Antibodies are divided into five major classes, IgM, IgG, Iga, IgD, and IgE, based on their constant region structure and immune functions.

IgG antibody function :

IgG provides long-term protection because it persists for months and years after the presence of the antigen that has triggered their production. IgG protects against bacteria, viruses, neutralizes bacterial toxins, triggers complement protein systems, and binds antigens to enhance the effectiveness of phagocytosis.

IgM antibody function :

IgM is involved in the ABO blood group antigens on the surface of RBCs. IgM enhances ingestions of cells by phagocytosis.

IgA antibody function :

The main function of IgA is to bind antigens on microbes before they invade tissues. It aggregates the antigens and keeps them in the secretions so when the secretion is expelled, so is the antigen. IgA is also the first defense for mucosal surfaces such as the intestines, nose, and lungs.

IgE antibody function :

IgE bind to mast cells and basophils which participate in the immune response. Some scientists think that IgE’s purpose is to stop parasites.

IgD antibody function :

IgD plays a role in the induction of antibody production.


The main role of the immune system is to recognize the pathogen, respond to the foreign antigens, and memorize them.


These are the organs where the maturation and proliferation of lymphocytes take place.
These are further divided into two types:

  1. Primary lymphoid organs: This comprises of bone marrow and thymus, where T-lymphocytes and the B-lymphocytes mature and acquire their antigen-specific receptors.
  2. Secondary lymphoid organs: It comprises of lymph nodes, spleen, and Mucosa Associated Lymphoid Tissue (MALT). After maturation of the T- lymphocyte and the B-lymphocyte, they migrate here via blood vascular and lymphatic system, where they undergo differentiation.


A vaccine is generally a half-killed or weakened disease-causing pathogen that is then given to the healthy individual through injection or drops, which has the ability to generate an immune response but not cause any disease or doesn’t have the ability to spread in the body. This causes acquired immunity against the disease-causing pathogen. This is called as vaccinisation or immunisation.
The concept of vaccinisation is based on the ‘memory’ of the immune system. Our immune system has the ability to recognize the pathogen if it has once been already spotted and antibodies have been created by our body.
So when the same pathogen enters our body, it is immediately spotted by the lymphocytes, and the antibodies are produced almost instantly given a quick response.


It is the process of replacement of diseased tissue with healthier ones. Various factors are involved in transplanting an organ from a donor to a recipient such as tissue matching, immunosuppression, the immune response generated in the recipient. T-cells play a major role in the process of rejection.


Antigens are the substance majority made of protein that has the capability to stimulate the production of antibodies. Antibodies are protein molecule that inactivates the antigen. They are also called immunoglobulins. Lymphoid organs are the place where the maturation of lymphocytes takes place. Vaccine is introduced into our body to prepare antibodies against certain pathogens. While organ transplant has its own pros and cons.

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