Studies on antigenic competition. Effect of antigen dose on the immune response of mice injected simultaneously with human serum albumin and ferritin.

Human serum albumin (HSA) and ferritin in Freund's incomplete adjuvant (FIA) were injected simultaneously, intraperitoneally into mice in various dose/ratios. The degree of suppression of the primary and secondary immune responses to a small dose of HSA was dependent on the dose of ferritin injected simultaneously. A totally suppressed primary response was associated with a secondary response which only attained the level of a primary response to HSA in FIA. Similar results were obtained in experiments in which a constant dose of ferritin and varying amounts of HSA were injected simultaneously in FIA into mice. Suppression of the immune response to alum-precipitated HSA in the presence of soluble ferritin was not as striking as when the antigens were injected with FIA. Nevertheless, suppression of the primary response was again associated with a reduced secondary response. The results are discussed in the context of the possible mechanism(s) of antigenic competition.