LYMPHOCYTE-DEPENDENT INHIBITION OF GROWTH OF VIRULENT MYCOBACTERIUM-TUBERCULOSIS H37RV WITHIN HUMAN MONOCYTES - REQUIREMENT FOR CD4(-CELLS IN PURIFIED PROTEIN DERIVATIVE-POSITIVE, BUT NOT IN PURIFIED PROTEIN DERIVATIVE-NEGATIVE SUBJECTS() T)

Protective human immunity to Mycobacterium tuberculosis (M. tb) has pr oven difficult to characterize, in part because of technical obstacles to in vitro infection of human cells with virulent M. tb. We establis hed a reproducible method of infecting human monocytes (MN) with the v irulent M. tb strain H37Rv that did not reduce MN viability. TNF-alpha had no effect on replication of H37Rv within BM, and IFN-gamma mediat ed only a 1.9-fold reduction in bacterial growth, In contrast, nonadhe rent cells (NAC) from purified protein derivative (PPD)-positive and P PD-negative subjects reduced intracellular growth of H37Rv by 6- and 1 0.6-fold, respectively (p = 0.007 and p = 0.005), CD4(+) T cells were essential to growth inhibition mediated by NAC of PPD-positive subject s, whereas containment of M. tb by NAC of PPD-negative subjects did no t require CD4(+) cells. CD8(+) T cells did not contribute to protectio n mediated by NAC of either group, Supernatants of cocultured H37Rv-in fected MN and NAG only partially reduced intracellular growth of M. tb despite containing nanogram concentrations of TNF-alpha and IFN-gamma . Neutralizing antibodies to TNF-alpha, IFN-gamma, and IL-12 failed to affect the NAC-mediated growth limitation, NAC treated with emetine r etained approximately 40% of their capacity to contain intracellular H 37Rv, however. These studies indicate that protective human recall res ponses to M. tb are mediated primarily by CD4(+) T cells, whereas CD4( -)CD8(-) lymphocytes may contribute to innate immunity to M. tb. The a bility of NAC to activate M. tb-infected MN is only partly attributabl e to soluble mediators and may also involve contact-mediated mechanism s,.