Analysis of monoclonal antibodies specific for the γδ TcR

Abstract γδ T cells in ruminants can be subdivided in two or more subpopulations on the basis of the expression of surface antigen WC1, which can exist in different isoforms. In this study, 18 monoclonal antibodies (mAbs) submitted to the Third International Workshop that were predicted to react with γδ TcR molecules were analysed and expression of their antigens was investigated on the different γδ T cell subpopulations. A set of control mAbs positive for TcR1 (86D), BoCD3 (MM1A), WC1 (B7A1, BAQ4A, CACTB32A, and BAQ89A) was included for comparative studies. Previous investigations demonstrated eight of the mAbs immunoprecipitated peptides with apparent M r s of 37 and/or 47 kDa, indicating they recognized determinants on the T cell receptor, TcR1. Two color flow cytometric analyses in the present study demonstrated the mAbs formed three groups; group 1, a set of mAbs that recognize TcR1 determinants expressed on all γδ T cells and groups 2 and 3, sets of mAbs that recognize TcR1 determinants on some γδ T cells: TcR1-N6 and TcR1-N7 respectively. mAbs from the latter groups define families of TcR1 molecules that express either one or both of the determinants. These antigenically distinct forms of TcR1 are expressed in equal proportion on the two γδ T cell populationss that express one of the mutually exclusive isoforms of WC1, WC1-N3 and WC1-N4. The data indicate usage of the mAb-defined families of the γδ TcR is primarily restricted to the WC1 + subpopulation of γδ T cells. However, a small subpopulation of CD2 + , WC1 − γδ T cells expresses a form of TcR1 positive for the determinant TcR1-N6.