Antigenic Characteristics

There are some chemical entities abundantly found in the microbial cells known as
fact, antigens refer to a
protein or an oligosaccharide marker strategically located upon the surface of
cells which critically identifies the cell as
self 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, if
necessary; and stimulates cytotoxic responses by
granulocytes, monocytes, and lymphocytes.
It is, however, pertinent to state here that the very
antigenic characterization
of a microorganism
bears an immense practical significance. It has been duly observed that as soon as the ‘
’ enter the animal body, the latter quickly responds to their respective antigens due to the formation
of particular blood serum proteins known as
antibodies, which eventually get bound to the corresponding
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
microorganisms 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 this
antigen-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
) one may most conveniently identify the other with great ease.
Example: Identification of typhoid organism :
The typhoid bacterium antibody when duly
mixed with a
suspension of unknown bacterial cells, and consequently a positive reaction takes place,
one may safely infer that the
bacterial 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 cells
not of the typhoid bacterium but may belong to certain other bacterial species.