REGULATION OF EXPRESSION OF THE T CELL WC1 CO-RECEPTOR AND PATTERN RECOGNITION RECEPTOR MULTIGENE FAMILY

WC1 molecules are hybrid PRR/co-receptors exclusively expressed on gd T cells of ruminants while humans and mice have related receptors. Bovine WC1 molecules bind pathogens directly and specifically and augment TCR-mediated signals. Using NGS, we found all 13 WC1 genes transcribed by blood gd T cells with no significant differences at birth although by adulthood the relative proportions of transcripts was somewhat altered perhaps attributable to immunological experience. WC1+ gd T cells form two main subpopulations in blood, WC1.1 and WC1.2, distinguished by reactivity with various anti-WC1 mAbs. Their WC1 molecules also differ in their ability to bind particular microbes suggesting the WC1 molecules expressed by a gd T cell may determine its antigen specificity. Although it was clear that the WC1+ subpopulations differed in WC1 gene expression we did not know the expression of WC1 genes by individual gd T cells. Thus 78 gd T cell clones from flow-cytometrically purified WC1+ subpopulations were generated and evaluated by qRT-PCR. The majority of gd T cell clones transcribed 1 to 4 WC1 genes and, while overlap of some transcripts occurred between the two subpopulations, 80% of clones that were generated in response to Leptospira stimulation had transcripts for a WC1 molecule known to bind Leptopsira which was significantly higher than for non-responsive clones We found WC1 molecules are not detected on thymocytes prior to the gd TCR and that the two WC1+ subpopulations are at a similar ratio in thymus as in blood. Using ChIP, we showed that Sox13, an important transcription factor for gd T cell development, differentially occupied WC1 gene loci in the WC1.1+ versus WC1.2+ cells. Using qRT-PCR and immunofluorescence, we evaluated transcription factors critical to development and effector functions of T lymphocytes as well as cytokines and the gd T cell subset marker CD27 in the two subpopulations. WC1.1+ cells showed significantly higher levels of transcription for CD27, as well as higher transcription and protein for Tbx21 and IFNg than WC1.2+ cells; the latter had higher levels of transcripts for Rorc and Il17a. This suggests a tendency for a Tgd1-like phenotype versus Tgd17-like phenotype, respectively