CD4+ T Cell Clones Producing both Interferon-γ and Interleukin-10 Predominate in Bronchoalveolar Lavages of Active Pulmonary Tuberculosis Patients

The pattern of cytokine production in T cell clones derived from bronchoalveolar lavages (BAL) of active pulmonary tuberculosis (TB) patients was analyzed in clones obtained by limiting dilution procedures which expand with high efficiency either total T lymphocytes, independently of their antigen-recognition specificity, or Mycobacterium tuberculosis-specific T cells. BAL-derived clones, representative of CD4+ cells from five patients with active TB, produced significantly higher amounts of IFN-γ than BAL-derived CD4+ clones from three inactive TB donors or four controls (with unrelated, noninfectious pathology). Average IL-4 and IL-10 production did not differ significantly in the three groups. Although these data suggest a predominant Th1 response to M. tuberculosis infection in the lungs, the majority of BAL-derived CD4+ clones produced both IFN-γ and IL-10 and the percentage of clones with this pattern of cytokine production was significantly higher in clones derived from BAL of active TB patients than from controls. Only rare clones derived from peripheral blood (PB)-derived CD45RO+ CD4+ T cells of both patients (nine cases) and controls (four cases) produced both IFN-γ and IL-10; instead, the IL-10-producing clones derived from PB T cells most often also produced IL-4, displaying a typical Th2 phenotype. Higher average amounts of IFN-γ and IL-10 were produced by BAL-derived CD8+ clones of four active TB patients than of four controls, although the frequency of CD8+ clones producing both IFN-γ and IL-10 was lower than that of CD4+ clones. The M. tuberculosis-specific BAL-derived T cell clones from three active TB patients were almost exclusively CD4+ and produced consistently high levels of IFN-γ often in association with IL-10, but very rarely with IL-4. Unlike the BAL-derived clones, the M. tuberculosis-specific clones derived from PB CD45RO+ CD4+ T cells of three different active TB patients and two healthy donors showed large individual variability in cytokine production as well as in the proportion of CD4+, CD8+, or TCR γ/δ+ clones. These results indicate the predominance of CD4+ T cells producing both the proinflammatory cytokine IFN-γ and the anti-inflammatory cytokine IL-10 in BAL of patients with active TB.