Question

Antibodies are going to come in contact with an antigen and create an interaction. Please choose three and discuss what types of situations they would be present in.

Answer 1

Antigen and antibody combine specifically to each other to form antigen antibody complex. These reaction form the basis for detection of infectious agents and some non specific antigen like enzymes.

Antigen antibody reaction occurs as

Precipitation reaction: here when a soluble antigen reacts with its antibody in presence of an electrolyte in a particular temperature and pH, it forms an insoluble precipitate of antigen antibody complex. The precipitation reaction can occur in liquid and gel.

Agglutination reaction: when an antigen is mixed with its antibody in the presence of an electrolyte at a suitable temperature and pH, the particles may get agglutinated. The presence of agglutinating antibodies can be determined by slide agglutination method. Widal test for typhus fever is an example for tube agglutination method.

Enzyme linked immunosorbent assay ELISA: the ligand used here is a molecule which can detect the antibody and it is covalently bonded to enzyme like peroxidase, betagalactosidase, alkaline phosphatase etc. They are simple and sensitive method.