Antibodies are circulating multifunctional soluble glycoprotein which are produced by the plasma cells mainly the plasma B-cells in response to an antigen. These proteins are known as globulin for their globular structure. These are also known as immunoglobulin and play the key role in our immune system. It performs various function but the main function of antibody is to maintain our immune responses.
There are mainly five types of immunoglobulins are present in our body, these are: Ig-G, Ig-M, Ig-A, Ig-D, and Ig-E.
Function of Antibody: Antibody has various function in our immune system but the primary function of antibody is to bind with the specific antigen. Antibody also contain two portions Fab (fragment of antigen binding) which can bind with the antigen and Fc (Fragment of Crystallizable) which induces biological effector mechanism.
AGGLUTINATION: It is one of the most important function done by the interaction of antibody to the antigen. The antibodies present on the blood plasma interact with specific antigen and form antigen antibody complex. This complex forms a lattice structure which is unable to remain in the suspension and sediment, which protect our body from infectious antigen. This process of agglutination is mainly done by IgM antibody. IgM antibody can make the lattice structure more easily for its pentameric broad structure.
OPSONIZATION: Antibodies play a vital role in opsonization. They recognize the antigenic particles and attached with them and form antigen-antibody complex. These complexes are easily recognized by the phagocytic cells and the phagocytosis of the antigenic particle occur. For enhancing the phagocytosis process or for doing opsonization, antibodies are also called opsonin.
ANTIBODY DEPENDENT CELL MEDIATED CYTOTOXICITY: Fab part of the IgG binds with the receptor of target cell such as micro-organism or tumor cells and Fc binds with the specific receptor of granular lymphocytic cells like Natural killer cells. Activated NK cells release perforin and granzyme which causes lysis of the target cells.
BLOOD GROUPPING: For having the function of agglutination or the interaction between the antigen and antibodies present in the blood plasma, our blood groups are divided into different classes.
COMPLEMENT ACTIVATION: 20 serum proteins present in the blood plasma which are known as complement proteins are activated by antibodies. The complement complexes are activated in cascade manner which induces the inflammatory reaction and finally brings about inflammation and lysis.