FREQUENCIES OF IFN-GAMMA-PRODUCING AND IL-4-PRODUCING CELLS DURING MYCOBACTERIUM-BOVIS BCG INFECTION IN 2 GENETICALLY SUSCEPTIBLE MOUSE STRAINS - ROLE OF ALPHA BETA T-CELLS AND NK1.1 CELLS/

Frequencies of IFNgamma- and IL-4-producing spleen cells in response t o Mycobacterium bovis BCG infection were determined in C57BL/6 and BAL B/c mice. Both mouse strains express equal innate susceptibility to M. bovis BCG (Bcg(5)), but differ in their NK1.1 and T-cell activities. M. bovis BCG infection induced higher frequencies (f approximate to 1/ 500) of antigen-induced IFNgamma-secreting spleen cells in C57BL/6 mic e as compared to BALB/c mice (f approximate to 1/8000). Concanavalin A stimulated almost equal numbers of IFNgamma-secreting cells in both m ouse strains (f approximate to 1/50). Treatment with anti-NK1.1 mAb of M. bovis BCG-infected C57BL/6 mice did not alter frequencies of IFNga mma-secreting cells. Equally. low numbers of antigen-induced IL-4-prod ucing cells (f approximate to 1/3000) were determined in both C57BL/6 and BALB/c mice during M. bovis BCG infection and treatment of C57BL/6 mice with anti-NK1.1 mAb had no measurable effect on IL-4 producers. Finally, frequencies of IFNgamma-producing cells were markedly reduced (10-fold) in M. bovis BCG-infected TCR-beta(-/-) gene deletion mutant s as compared to their heterozygous controls. Our findings verify that M. bovis BCG infection primarily induces IFN gamma-secreting alpha/be ta T cells of TH1 type and show that the frequencies of these IFNgamma producers differ in the two Bcg(5) mouse strains C57BL/6 and BALB/c.