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Generation of functional murine macrophage lines employing a helper-free and replication-defective SV40-retrovirus: cytokine-dependent growth.

By using a helper-free and replication-defective recombinant retrovirus encoding the SV40 early antigens (MV40), we have established continuous macrophage (M phi) lines. All of the lines were nonproducer M phi's with differentiated M phi functions such as phagocytosis, cytotoxicity, and IL-1 and TNF production. To determine the effects of several cytokines on growth of mature M phi's, the responsiveness of these established M phi lines to various cytokines was investigated in methylcellulose culture. Their response patterns to several cytokines alone and in combination were different, implying that there might be mature M phi subpopulations with distinct growth profiles regulated by several cytokines. On the other hand, all of the lines efficiently yielded a number of colonies in response to interleukin-4 (IL-4) alone. Moreover, IL-4 cooperated with interleukin-3 (IL-3) to enhance colony formation of all the lines. A similarly synergistic effect was observed in combination of IL-4 and macrophage-colony stimulating factor (M-CSF) in almost all the lines. Similar results were obtained with colony formation of fresh thioglycolate-induced M phi's. These observations suggested that IL-4 was involved in growth of mature M phi's. Our present results suggest that the helper-free and replication-defective MV40 is of use to obtain continuous and functional cell lines from primary M phi's.