Complement: Effects of C1 Binding Affinity on the Efficiency of the C2 Reaction

[摘要] A variable amount of the C1 will dissociate from IgG-sensitized EAC14 at 30°C, µ = 0.065, depending on the relative amounts of antibody and C1 employed. for this reason, use of 30°C and µ = 0.065 for reacting C2 with IgG-sensitized EAC14 is inefficient, particularly with low IgG concentrations. Decreasing the ionic strength to 0.032 prevents dissociation of weakly-bound C1 during the C2 reaction at 30°C, and thus gives optimal results. Similar but not quite as good results can be obtained by adding 100 to 200 molecules of IgM anti-Forssman antibody/cell. It is suggested that this added IgM may function by capturing C1 which dissociates from IgG-SAC14 at 30°C, µ = 0.065. The resulting IgM-SAC1 could activate C2 molecules which then could bind to the IgG-SAC4, converting them to IgG-SAC42 which in turn could react with C3 and later components.Excessive amounts of IgM (1000 to 10,000 molecules/cell under the conditions employed here) can reduce the efficiency of the reaction with C2, perhaps by raising the C1 binding affinity above some optimal level and/or by taking control of some of the C4 sites away from the more efficient IgG antibody molecules. Given a relatively constant number of molecules of C1/cell, IgM-sensitized EAC14 show a progressive decrease in C2 reaction efficiency with increasing amounts of IgM/cell over a 100-fold range of SA/SAC1 ratios.

[学科分类] 生物科学（综合）