In order to estimate toxigenity of diphtheria agents obtained from patients the cultures were inoculated on Petri dish with nutrient agar on either side of a filter paper strip that was put into the centre and moistened with antidiphtheric antitoxic serum. After incubation of inoculations in agar the strip-like areas of medium turbidity were found between separate cultures and the strip of filter paper. What immunological reaction was conducted?

Answer options

1. Precipitation gel reaction
2. Coomb’s test
3. Rings precipitation reaction
4. Opsonization reaction
5. Agglutination reaction

Explanation

In Precipitation in agar (Precipitation gel reaction): antibody is incorporated into agar and antigen is inoculated i.e. antibody is the antidiphtheritic antitoxic serum and the antigen is the diphtheria agent, inoculated in the nutrient agar. Antigen and antibody are placed in different wells in agar and allowed to diffuse and form concentration gradients. Where optimal proportions occur, lines of precipitate form. This method indicates whether antigens are identical, related but not identical, or not related. Areas of medium turbidity indicate where the antibody specific for the antigen has cross-linked.