The course of LCMV infection in euthymic and athymic mice pretreated with immunomodulatory agents.

Balb/c (euthymic) and nu/nu (athymic) mice were treated intraperitoneally with TP-4 (a synthetic tetrapeptide, thymopoietin sequence analog) or with Mannozym (1% zymosan suspension), and were infected intracerebrally with LCM virus. Both of the agents contributed to the development of fatal choriomeningitis, consequently stimulated the cellular immune response in euthymic mice, but the athymic mice either treated or not, survived the infection, consequently the agents had no effect on the course of LCM virus infection. Both agents exerted a thymus-dependent cellular immune response stimulating effect. That is, an immunostimulatory effect can be realized only in the presence of the thymus or the T-dependent lymphoid system.