B. Ouchterlony gel diffusion (a precipitation reaction)

This is an example of a precipitation reaction between antibodies and soluble antigens, in this case, protein. The bivalent antibodies will cross-link the soluble antigen to form a lattice network and yield a visible precipitate. As with any antibody-antigen reaction, the antibody must specifically recognize the antigen. In this experiment, bovine serum albumin (BSA) will be used as the soluble antigen and anti-BSA antiserum as the antibody preparation.

The Ouchterlony gel diffusion test is done in an agar gel prepared with cut out wells for the antigen and antibody. In today's experiment, the antibody is placed in the center well and varying concentrations of antigen are placed in the outer wells. The agar allows the antigen and antibody to diffuse freely out from the wells to establish a concentration gradient. The antibody is most concentrated close to the center well and becomes less concentrated further away from the well. This is also true for the antigen in the outer wells. At the points where the concentrations of both antigen and antibody are optimal, the lattice network will form into a visible band of white precipitate. These bands are immobilized in the gel. This procedure permits quantitative and qualitative characterizations of the antibody/antigen interaction.

Rachel Watson, M.S.
AG 5010
766-3524
Cell: 307-760-2942
rwatson@uwyo.edu