T-dependent production and activation of mononuclear phagocytes during murine BCG infection

Mice infected with a high dose of viable Bacillus Calmette Guerin (BCG) intravenously offer an interesting model to study regulatory functions of T cells on hemopoiesis. The proposition that T lymphocytes may play such a regulatory role was tested in nu/nu and two genetically different strains of mice: while the hemopoiesis of C3H/He mice remained unchanged during BCG injection, that of infected C57BL/6 mice was rapidly and transiently modified towards increased production of phagocytes at the expense of the erythroid lineage. The number of BCG-specific T cells present in C57BL/6 bone marrow was 50-100 higher than that determined in C3H/He mice. Moreover, between day 0 and 5 of infection the majority of BCG-specific T cells in C57BL/6 animals were of the L3T4+ Lyt2- surface phenotype. An attempt was made to identify the nature of the T cell product(s) able to activate young bone marrow-derived macrophages to render them non-permissive to growth of BCG.