Control of hemopoiesis in mice by sensitized L3T4+ Lyt2-lymphocytes during infection with bacillus Calmette-Guérin.

When injected intravenously with bacillus Calmette-Guérin (BCG; 10(7) viable units), C57BL/6 mice rapidly develop a transient anemia associated with an increased number of granulocytes and monocytes, whereas C3H/He mice do not. Because these two features are lacking in C57BL/6 nude mice we postulated that T lymphocytes can regulate hemopoiesis during infection. To assess further the role in hemopoiesis of T lymphocytes present in bone marrow of C57BL/6 and C3H/He mice, the frequency of BCG-specific T lymphocytes and their surface marker phenotype were determined by limiting dilution analysis and use of monoclonal antibodies. The number of BCG-specific T lymphocytes was estimated to be 50- to 100-fold higher in bone marrow of C57BL/6 than in that of C3H/He mice. Although L3T4+ Lyt2-and L3T4- Lyt2+ BCG-specific T lymphocytes were generated in mice of both strains, in C57BL/6 mice L3T4+ cells were induced preferentially from day 1 through day 5 after infection in correlation with hemopoietic changes. The relation between T-cell immune response and hemopoietic changes was substantiated by results obtained after in vivo treatment with monoclonal antibodies. Selective depletion of L3T4+ T cells by in vivo injection of anti-L3T4 monoclonal antibodies (GK 1-5) inhibited the development of the anemia and the related increased production of phagocytes in C57BL/6 mice receiving BCG.