Characterization of the porcine γδ T‐cell receptor structure and cellular distribution by monoclonal antibody PPT27

The T‐cell receptor (TCR) is the critical structure involved in antigen recognition of T lymphocytes. Although the pig has a large proportion of circulating T lymphocytes bearing the γδ TCR, their study has been impeded due to the lack of specific antibodies. Here a monoclonal antibody (mAb) PPT27 directed to γδ TCR is described. Flow cytometry analyses showed that the mAb recognized a subset of T lymphocytes of which the majority expressed no CD2, CD4 and CD8 whilst the minority bore CD2 and CD8. The mAb precipitated a protein of 86 000 MW under non‐reducing conditions and a doublet of 43 000 MW under reducing conditions from peripheral blood T lymphocytes lysed in nonidet P‐40 buffer, whilst it precipitated the CD3–TCR complex from the cells lysed in digitonin. Further analysis revealed that the antibody recognized the majority, but not all, of the γδ T cells, suggesting that there may be more isotypes of γδ TCR than currently believed. The antibody was unable to stimulate γδ T cells to proliferate in vitro, suggesting that these cells are activated by a different activation mechanism from that of αβ T cells.