Antibodies in animals
Antibodies are the gamma globulins or immunoglobulins made up of a combination of light and heavy polypeptide chains. Each heavy chain is paralleled by a light chain at one of its end, which form the variable portion.
This variable region with both light and heavy chains provides very specific binding site to the specific antigen. Specific Antibodies differ from each other based on the different amino acid sequence in the light and heavy chains of the variable portion.
On the other hand the free ends of the two heavy chains form the constant portion of the antibody which establishes the properties like diffusibility, adherence to tissue and attachment to complement complex.
Mechanisms of action of antibodies
Agglutination in which antigens in the bacteria are bound by antibodies to form a clump. Precipitation in which the soluble antigen is rendered insoluble and precipitated.
Neutralization‚ to cover the binding site of the toxin thus makes the virus non-virulent. Lysis‚ by the lysosome following the attachment with the antibody with the cell membrane of the invaders.
Lymphocytes are motile, but not phagocytic in function. During viral infection, these cells come in contact with specific virus and release specific interferons‚ which inhibits the multiplication of that virus. Interferon also circulates throughout the body and protects other body cells from that virus.
NATURAL KILLER CELLS
Natural killer cells (also known as NK cells, K cells, and killer cells) are a type of lymphocyte (a white blood cell) and a component of innate immune system.
NK cells play a major role in the host-rejection of both tumours and virally infected cells.
These cells are cytotoxic and contain small granules in their cytoplasm with special proteins such as perforin and proteases known as granzymes.
When NK cells comes in close contact with target cells, perforin forms pores in the cell membrane of the target cell through which the granzymes and associated molecules enter, inducing apoptosis or death of the cell.
NK cells are activated in response to interferons or macrophage-derived cytokines and control viral infections.