Investigating the clonality and formation of memory populations of non-conventional NKp46+ CD3+ T-cells

Abstract

NKp46+ CD3+ T cells have been defined as a novel non-conventional T lymphocyte subset of cattle that express both NK cell and T cell receptors. It has been hypothesized that NKp46+ CD3+ cells may form a niche bridging the innate and adaptive immune response and there is now evidence they may play a role in the responses against Theileria parva and Mycobacteria. Thus, NKp46+ CD3+ cells may offer a novel population to target in vaccination strategies. In bovine, recent studies have shown that NKp46+ CD3+ cells can recognize and respond to autologous Theileria parva infected cells (TpM) and that NKp46+ CD3+ cell lines can be generated and maintained in vitro. Functional analysis has indicated that both NKp46 receptor and CD3 (i.e. TCR) cross-linking can lead to cell activation, however, the function of the T cell receptor is still not clear. The aim of this study is to analyze the TCR repertoire of TpM-stimulated NKp46+CD3+ populations to look for evidence of TCR selection that would indicate a role for TCR in mediating recognition of TpM. To address this aim, we use high resolution NGS TRB sequence analysis to compare the TCR repertoires observed in TpM-stimulated and non-specific stimulated NKp46+CD3+ populations derived from naïve and T. parva-immune animals. TpM specific-stimulated NKp46+CD3+ cell lines were successfully generated from naive and T. parva immunized cattle, but generation and maintenance of NKp46+CD3+ cell lines through use of non-specific stimulant was unsuccessful. The results of this study provide evidence of clonal selection in the T. parva-specific response of NKp46+ CD3+ T-cells and in 2 naïve animals highly overlapping TRB repertoires. From the current data it is confirmed that NKp46+CD3+ cells express a highly diverse TRB repertoire with no obvious and consistent overt bias for usage of particular TRBV or TRBJ genes.