Plasmacellular and granulomatous splenomegaly produced in rats by tin.

Two intravenous inoculations of metallic tin powder caused a striking, self-limited enlargement of the spleen up to five or six times its normal size. In addition to epithelioid cell granulomas in response to the foreign particles, the spleen contained extensive accumulations of plasmablasts, plasma cells, and plasma cells containing Russell bodies. The proliferative activity of the immature plasma cells was indicated by the high incidence of mitoses and cells labeled with tritiated thymidine. In contrast, the granulomas had no mitoses or labeling. A single intravenous injection of tin usually produced little or no reaction in the spleen despite an abundance of tin particles. Two intravenous injections or one intravenous and one intraperitoneal inoculation were much more effective. Experiments on route, interval, and dose suggested that the first dose of tin prepared the spleen in some manner while the second dose actually elicited the reaction. Pertussis vaccine or glucan could substitute for one of the tin injections. This new model is of interest for the study of plasma cell hyperplasia and also for revealing the pathogenic potential of metallic tin.