Immune reactions in polysaccharide media. Experiments with specific antibodies of different affinities for serum albumin.

Rabbit antibody fractions of different affinities for human serum albumin were prepared by an immunosorbent technique. The fractions were used in studies on the enhancement of the precipitin reaction by polymers. Dextran increased the immune precipitation to about the same extent regardless of whether antibodies with high and low affinities were used. The effect should considerably facilitate the detection of antibodies with low precipitating ability in immunological assays. The results are discussed in terms of a steric-exclusion mechanism.