Growth of Trypanosoma musculi in cultures of murine spleen cells and analysis of the requirement for supportive spleen cells.

Growth of Trypanosoma musculi in vitro has been achieved. The number of parasites increased by more than 1,500-fold in less than 8 days under the most suitable conditions. The rate and magnitude of growth was comparable to that which occurs in inoculated murine hosts. Maximum growth was displayed in cultures composed of RPMI 1640 medium supplemented with fetal calf serum, murine spleen cells, and foreign erythrocytes (sheep). No growth occurred in the absence of spleen cells. The adherent, macrophage-rich population supported parasite growth much better than did the nonadherent population. Parasite growth was excellent in the presence of irradiated spleen cells or of cells from thymectomized, irradiated, bone marrow-reconstituted mice. The important cells appeared to be macrophages. The beneficial effect of sheep erythrocytes probably resulted from preoccupation or stimulation of phagocytes. Soluble substances released by spleen cell cultures promote parasite growth, as was shown by experiments with double-compartment culture vessels. The utility of this culture system for analysis of host immune responses against the trypanosome was demonstrated.