Primary responses of human T cells to mycobacteria: a frequent set of γ/δ T cells are stimulated by protease‐resistant ligands

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Abstract
T lymphocyte subsets expressing either T cell receptor α/β or γ/δ were selected from human peripheral blood T cells and proliferative responsesto molecular mass‐fractionated mycobacterial lysates were determined. α/β T cells primarily responded to fractions > 30 kDa whereas γ/δ Tcells preferentially reacted to fractions < 3 kDa. Protease digestion abolished the stimulating activities for α/β T cells, confirming that α/β Tcells respond to protein components. In contrast, components recognized by γ/δ T cells proved resistant to protease digestion. In limiting dilution studies, frequencies of proliferating γ/β T cells remained virtually unaltered by protease treatment of stimulating lysates, while those of α/β T cells became almost undetectable. Furthermore, only few γ/δ T cells responded to the 65‐kDa heat‐shock protein. Our data indicate that, unlike α/β T cells, γ/δ T cells respond to mycobacterial components which are resistant to vigorous protease digestion.