Mouse gammadelta T cells are capable of expressing MHC class II molecules, and of functioning as antigen-presenting cells.

Although human and bovine gammadelta T cells were shown to express MHC class II antigen and function as APCs, attempts to determine if mouse gammabeta T cells have similar functions remained unsuccessful. We now show that gammadelta T cells derived from immunized mice also can be induced to express MHC class II and co-stimulatory molecules after activation in vitro, and are capable of antigen presentation. Using highly purified gammadelta T cells, we found that, unlike human gammadelta T cells, the expression of MHC class II molecules by mouse gammadelta T cells is limited to newly activated cells. Highest levels of MHC class II expression were seen on activated gammadelta T cells that had lost most surface-expressed gammadelta TCR while exhibiting increased levels of intracellular gammadelta TCR. In the absence of further stimulation, MHC class II expression gradually declined with the gammadelta T cells regaining their surface TCR. We also show that cytokine-activated gammadelta T cells can also express MHC class II antigen and exercise antigen-presenting activity.