• Martin Busch, Christian Herzmann, Stephanie Kallert, Andreas Zimmermann, Christoph Höfer, Daniel Mayer, Sebastian F Zenk, Rainer Muche, Christoph Lange, Barry R Bloom, Robert L Modlin, Steffen Stenger, and TBornotTB Network.
• 1 Institute for Medical Microbiology and Hygiene, University Hospital Ulm, Ulm, Germany.
• Am. J. Respir. Crit. Care Med. 2016 Aug 1; 194 (3): 345-55.

RationaleThe development of host-targeted, prophylactic, and therapeutic interventions against tuberculosis requires a better understanding of the immune mechanisms that determine the outcome of infection with Mycobacterium tuberculosis.ObjectivesTo identify T-cell-dependent mechanisms that are protective in tuberculosis.MethodsMulticolor flow cytometry, cell sorting and growth inhibition assays were employed to compare the frequency, phenotype and function of T lymphocytes from bronchoalveolar lavage or the peripheral blood.Measurements And Main ResultsAt two independent study sites, bronchoalveolar lavage cells from donors with latent tuberculosis infection limited the growth of virulent Mycobacterium tuberculosis more efficiently than those in patients who developed disease. Unconventional, glycolipid-responsive T cells contributed to reduced mycobacterial growth because antibodies to CD1b inhibited this effect by 55%. Lipoarabinomannan was the most potent mycobacterial lipid antigen (activation of 1.3% T lymphocytes) and activated CD1b-restricted T cells that limited bacterial growth. A subset of IFN-γ-producing lipoarabinomannan-responsive T cells coexpressed the cytotoxic molecules perforin, granulysin, and granzyme B, which we termed polycytotoxic T cells. Taking advantage of two well-defined cohorts of subjects latently infected with Mycobacterium tuberculosis or patients who developed active disease after infection, we found a correlation between the frequency of polycytotoxic T cells and the ability to control infection (latent tuberculosis infection, 62%; posttuberculosis patients, 26%).ConclusionsOur data define an unconventional CD8(+) T-cell subset (polycytotoxic T cells) that is based on antigen recognition and function. The results link clinical and mechanistic evidence that glycolipid-responsive, polycytotoxic T cells contribute to protection against tuberculosis.

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