Specific recognition of mycobacterial protein and peptide antigens by γδ T cell subsets following infection with virulent Mycobacterium bovis

JL McGill, RE Sacco, CL Baldwin, JC Telfer… - The Journal of …, 2014 - journals.aai.org
JL McGill, RE Sacco, CL Baldwin, JC Telfer, MV Palmer, W Waters
The Journal of Immunology, 2014journals.aai.org
Promoting effective immunity to Mycobacterium bovis infection is a challenge that is of
interest to the fields of human and animal medicine alike. We report that γδ T cells from
virulent M. bovis–infected cattle respond specifically and directly to complex, protein, and
nonprotein mycobacterial Ags. Importantly, to our knowledge, we demonstrate for the first
time that bovine γδ T cells specifically recognize peptide Ags derived from the mycobacterial
protein complex ESAT6: CFP10 and that this recognition requires direct contact with APCs …
Abstract
Promoting effective immunity to Mycobacterium bovis infection is a challenge that is of interest to the fields of human and animal medicine alike. We report that γδ T cells from virulent M. bovis–infected cattle respond specifically and directly to complex, protein, and nonprotein mycobacterial Ags. Importantly, to our knowledge, we demonstrate for the first time that bovine γδ T cells specifically recognize peptide Ags derived from the mycobacterial protein complex ESAT6: CFP10 and that this recognition requires direct contact with APCs and signaling through the T cell Ag receptor but is independent of MHC class I or II. Furthermore, we show that M. bovis infection in cattle induces robust IL-17A protein responses. Interestingly, in contrast to results from mice, bovine CD4 T cells, and not γδ T cells, are the predominant source of this critical proinflammatory mediator. Bovine γδ T cells are divided into subsets based upon their expression of Workshop Cluster 1 (WC1), and we demonstrate that the M. bovis–specific γδ T cell response is composed of a heterogeneous mix of WC1-expressing populations, with the serologically defined WC1. 1+ and WC1. 2+ subsets responding in vitro to mycobacterial Ags and accumulating in the lesions of M. bovis–infected animals. The results described in this article enhance our understanding of γδ T cell biology and, because virulent M. bovis infection of cattle represents an excellent model of tuberculosis in humans, contribute to our overall understanding of the role of γδ T cells in the mycobacterial-specific immune response.
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