Protective role of γ/δ T cells and α/β T cells in tuberculosis

Tuberculosis is a chronic infectious disease which causes major health problems globally. Although acquired resistance crucially depends on α/β lymphocytes, circumstantial evidence suggests that, in addition, γ/δ T lymphocytes contribute to protection against tuberculosis. We have studied Mycobacterium tuberculosis infection in TcR‐δ‐/‐ or TcR‐β‐/‐ gene deletion mutants which completely lack γ/δ T cells or α/β T cells, respectively. Low inocula of M. tuberculosis led to death of TcR‐β‐/‐ mice and transient disease exacerbation in TcR‐δ‐/‐ mutants. Infection with higher inocula caused rapid death of TcR‐δ‐/‐ mice. The development of and bacterial containment in granulomatous lesions was markedly impaired in TcR‐β‐/‐, and less severly affected in TcR‐δ‐/‐ mutants. Mycobacteria‐induced IFN‐γ production by spleen cells in vitro was almost abolished in TcR‐β‐/‐ and virtually unaffected in TcR‐δ‐/‐ mice. Our data confirm the crucial role of α/β T cells in protection against established tuberculosis and formally prove a protective role of γ/δ T cells in early tuberculosis.