The immune response of mice to antigen in macrophages.

Peritoneal macrophages obtained following an injection of proteose peptone, and after uptake of haemocyanin were transferred to syngeneic hosts. Immunogenicity was tested by the capacity of macrophages containing the antigen to prime normal or irradiated (660–700 r) recipients for a secondary immune challenge. The immunogenicity of macrophages containing antigen depended on interaction with immunocompetent lymphoid cells since irradiated hosts were unresponsive unless normal lymphoid cells were also supplied. For optimal immune response the live macrophages had to gain access to lymphoid organs. Depending on the amount of antigen transferred with the macrophages, the recipient mice synthesized on secondary challenge 7S and/or 19S antibody. The kinetics of response to the antigen in macrophages were similar to those seen when using free soluble material except for some quantitative differences. Although the immune response was dependent on the total dose of antigen transferred with the macrophages, somewhat higher antibody titres were obtained with macrophages having a high antigen—cell ratio. Antigen in macrophages could elicit a secondary response in primed mice. The immunogenicity of macrophage-held haemocyanin was not impaired by X-irradiation of macrophage donors.