Increased production of plaque-forming cells in mouse lymph nodes following regional injection of a second antigen.

An analysis was made of the antibody response in the spleen and lymph nodes of mice to erythrocyte antigens injected under conditions which have been reported to cause antigenic competition. In the spleen, injection of a different erythrocyte antigen 2–4 days before the injection of a test antigen had little or no effect on the total number of cells or the number of plaque-forming cells (PFC) to the test antigen. Examination of the antibody response in opposite lymph nodes of a mouse made possible a comparison between two different conditions of antigen exposure within the same individual. In the lymph nodes, preceding the injection of the test antigen by an injection of a different erythrocyte antigen 2–4 days earlier led not to a decrease, but, on the contrary, to an increase in the number of plaque-forming cells to the test antigen. A similar increase in the number of plaque-forming cells per lymph node was observed for each of two test antigens, when these had been mixed and injected into the forefeet 24 hours after the injection of a different erythrocyte antigen.