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

Although human and bovine gamma delta T cells were shown to express MHC class II antigen and function as APCs, attempts to determine if mouse gamma delta T cells have similar functions remained unsuccessful. We now show that gamma delta 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 gamma delta T cells, we found that, unlike human gamma delta T cells, the expression of MHC class II molecules by mouse gamma delta T cells is limited to newly activated cells. Highest levels of MHC class II expression were seen on activated gamma delta T cells that had lost most surface-expressed gamma delta TCR while exhibiting increased levels of intracellular gamma delta TCR. In the absence of further stimulation, MHC class II expression gradually declined with the gamma delta T cells regaining their surface TCR. We also show that cytokine-activated gamma delta T cells can also express MHC class II antigen and exercise antigen-presenting activity.