There are some chemical entities abundantly found in the microbial cells known asantigens.
fact, antigens refer to aprotein or an oligosaccharide marker strategically located upon the surface of
cells which critically identifies the cell asself or non-self; identifies the type of cell, e.g., skin, kidney;
stimulates the production of antibodies, by B lymphocytes which will neutralize or destroy the cell, ifnecessary; and stimulates cytotoxic responses by
granulocytes, monocytes, and lymphocytes.
It is, however, pertinent to state here that the veryantigenic characterization of a microorganism
bears an immense practical significance. It has been duly observed that as soon as the ‘microbial
cells’ enter the animal body, the latter quickly responds to their respective antigens due to the formation
of particular blood serum proteins known asantibodies, which eventually get bound to the corresponding
antigens.Obviously, the antibodies are extremely specific for the respective antigens which categorically
persuade their actual formation. Taking critical advantage of the vital fact that various types
ofmicroorganisms do significantly possess various types of antigens ; and, therefore, antibodies find
their abundant utility and tremendous application as most vital tools for the precise as well as instant
identification of specific types of microbes.
In other words, one may regard thisantigen-antibody reaction very much similar to the ‘lock
and key arrangement’.Therefore, keeping in view the extremely critical as well as highly specific
nature of the said reaction, if one is able to decipher one segment of the ensuing system (antigen or
antibody) one may most conveniently identify the other with great ease.
Example: Identification of typhoid organism :The typhoid bacterium antibody when duly
mixed with asuspension of unknown bacterial cells, and consequently a positive reaction takes place,
one may safely infer that thebacterial cells are definitely those of the typhoid organism. In turn, if
there is no definite reaction taking place, one may draw a conclusion that these ensuing bacterial cellsare
not of the typhoid bacterium but may belong to certain other bacterial species.