On the mechanism of the ring zone effect obtained with the mixed haemadsorption technique. Studies with defined model systems.

Abstract

Studies on the ring zone effect obtained by the mixed haemadsorption technique on thyroid cultures with sera from patients with thyroid autoimmunity were continued in a model system that permitted a controlled variation of some relatively well defined and simple antigens (human serum albumin, HSA, dinitrophenyl‐human serum albumin, DNP‐HSA). Varying doses of these substances were conjugated to human monolayer cultures by the aid of bis‐diazotized benzidine. Reactions to the antigens were examined by the mixed haemadsorption technique using rabbit antisera against HSA and DNP. Ring zone effects were obtained with anti‐HSA sera only after prolonged immunization producing high anti‐HSA titres and only with a narrow range of relatively low HSA concentrations on the cultures. More antibody was eluted from cultures pre‐incubated with ring zone serum than with corresponding concentrations of filled zone serum. Rabbit ring zone anti‐HSA attached to HSA conjugated cultures was traced more effectively by anti‐gamma and anti‐Fc sera than by anti‐L chain sera, while filled zone anti‐HSA was traced equally effectively by all three types of antiglobulin. Anti‐DNP sera did not produce ring zones with any concentration of DNP‐HSA on the cultures or with any obtainable DNP saturation on the HSA molecules. On the other hand, half saturation or more of DNP on the HSA molecules turned the ring zones obtained with anti‐HSA into filled zones. These results were in agreement with those obtained on thyroid cultures and lend further support to the hypothesis that the ring zones are due to steric hindrance effects on the antibodies in densely crowded clusters of determinants representing several antigen specificities.