Interaction of γδ TCR with the WC1 hybrid co-receptor/pathogen recognition receptor in cattle.

Abstract

Listen

Translate article

Abstract Ruminants have a larger proportion of γδ T lymphocytes in blood compared to mice and humans. These lymphocytes are first responders to pathogens such as Leptospira and Mycobacterium. Bovine γδ T cells that respond to these pathogens express members of a unique γδ T-cell specific molecular family WC1 that are hybrid pattern recognition receptors and signaling co-receptors. Only γδ T cells that express WC1 molecules that bind to the pathogens selectively respond by proliferation and cytokine production. WC1 molecules have also been shown to augment signaling when co-crosslinked with the TCR but cannot signal on their own. Silencing WC1 through shRNA results in inhibition of the response to leptospira. Together these data indicate that WC1 is crucial for activation of the cells and we wished to further understand how the TCR interacts with WC1. The TCR is transcribed from a recombination of variable, joining, and diversity genes resulting in hundreds to millions of different possible sequences while the WC1 family has only 137 different pathogen-binding SRCR domains coded for by 13 genes. Yet only γδ T cells that express particular WC1 family members respond to leptospira suggesting it has primacy. We hypothesize that WC1 molecules co-localize with the TCR following binding of the pathogen. To test this hypothesis we used Imaging flow cytometry. Using FRET analysis we are able to determine that not only are the TCR and WC1 co-localized in the synapse following activation but they also are interacting closely within 9nm of each other. To evaluate the role of the TCR in dictating specificity of the response we are using next generation sequencing of transcripts coding for the TCR gamma and delta chains in leptospira-responsive cells.