A sub-population of circulating porcine γδ T cells can act as professional antigen presenting cells

A sub-population of circulating porcine γδ T cells express cell surface antigens associated with antigen presenting cells (APCs), and are able to take up soluble antigen very effectively. Functional antigen presentation by γδ T cells to memory helper T cells was studied by inbred pig lymphocytes immunised with ovalbumin (OVA). After removing all conventional APCs from the peripheral blood of immunised pigs, the remaining lymphocytes still proliferated when stimulated with OVA. When γδ T cells were further depleted, OVA specific proliferation was abolished, but reconstitution with γδ T cells restored proliferation. The proliferation was blocked by monoclonal antibodies (mAb) against MHC class II or CD4, and by pre-treatment of γδ T cells with chloroquine. These results indicate that a sub-population of circulating porcine γδ T cells act as APCs and present antigen via MHC class II.