γδ T cells present antigen to CD4+ αβ T cells

γδ and αβ TCR+ T cells share many properties and their interactions are likely to be coordinated and regulated. We provide evidence that cattle γδ T cells are able to present antigen to CD4+ T cells. To help elucidate their function γδ T cell lines were propagated for extensive characterization. Cells expressed high levels of MHC class II and production of costimulatory molecules as evidenced by the binding of a CTLA‐4 fusion protein and synthesis of CD80 transcripts. These properties and the presence of a well‐developed endosomal compartment indicated the cells might function as antigen‐presenting cells. Resting CD4+ T cells from calves immunized with ovalbumin or respiratory syncytial virus‐antigen proliferated in response to γδ T cells pulsed with antigen that appeared to be endocytosed via clathrin‐coated pits or specific receptors. J. Leukoc. Biol. 63: 707–714; 1998.