Q. 41 Define antigen and antibody. Name any two diagnostic kits based upon them.

An antigen is a foreign substance that elicits the immune response and results in the formation of an antibody.

Antibody is a protein that is synthesised by the body in response to an antigen.

Antigen and antibody shows high degree of specificity in binding to each other.

Two diagnostic kits based on antigen-antibody interaction are
(a) ELISA for HIV.
(b) Pregnancy test kits.