γ/δ T lymphocytes in Mycobacterium tuberculosis infection

Abstract

Background - Data on the percentage of γ/δ T lymphocytes in the peripheral blood of patients infected with Mycobacterium tuberculosis are few and contradictory. The percentage of γ/δ T lymphocytes in the peripheral blood of tuberculin positive and tuberculin negative patients with Mycobacterium tuberculosis infection and healthy controls was compared. Methods - Thirty six patients infected with Mycobacterium tuberculosis and 11 healthy controls were studied. Lymphocytes were separated, cytocentrifuged onto glass microscope slides, and reacted with anti-γ/δ monoclonal antibody. The percentage of γ/δ positive cells was determined by microscopic counting of 300 lymphocytes. Results - No difference was found in the percentage of γ/δ T lymphocytes between patients and controls. However, when the patients were divided into two groups according to reactivity or non-reactivity in the Mantoux skin reaction a higher percentage of γ/δ T lymphocytes was found in the peripheral blood of patients with tuberculin anergy than in tuberculin positive patients or controls. Conclusions - Higher γ/δ T cell counts are found in tuberculin negative patients with tuberculosis than in tuberculin positive patients or tuberculin positive controls. The high γ/δ T cell counts in tuberculin anergic patients may reflect a shift in the immune response in a Th2 direction characterised by increased antibody production and decreased cell mediated responses.