[Characteristics of Fc IgG receptors on the surface of formalinized sheep erythrocytes].

The binding of IgG molecules with sheep red blood cells (SRBC) was evaluated by a decrease in the serological activity of hyperimmune horse serum towards Pasteurella pestis capsular antigen. As in serological tests based on passive hemagglutination, low concentrations of red blood cells are commonly used, there was no danger of obtaining distorted results due to the nonspecific adsorption of IgG on the surface of SRBC. But for the objective evaluation of the results obtained in the determination of antibody affinity by the suspension method the use of an adequate control was necessary. Fab-fragments, in contrast to IgG, could not be extracted by red blood cells from the solution. The average number of Fc IgG receptors on the surface of one formalinized SRBC was about 60,000, and the affinity of these receptors somewhat varied, the average association constant being KO=10(6), (03) L/M.