Response of bovine γδ T cells to activation through CD3

Since the T cell receptor of gammadeltaT cells is associated with CD3 molecules, it is a reasonable postulate that signal transduction through CD3 would occur in gammadeltaT cells as it does in alphabetaT cells. However, while a small percentage of bovine gammadeltaT cells divided in cultures of peripheral blood mononuclear cells (PBMCs) in response to stimulation by anti-CD3 monoclonal antibody (mAb) the majority of viable gammadeltaT cells at the end of the culture period had not. This was assessed by carboxyfluorescein succinimidyl ester (CFSE) loading of cells and flow cytometric analysis here and previously [Res. Vet. Sci. 69 (2000) 275]. When intracytoplasmic staining for interferon-gamma (IFN-gamma) was also used here to assess activation through CD3, a small proportion of gammadeltaT cells (approximately 14%) produced IFN-gamma during the first 4 h of culture and by 72 h of culture that number had doubled. By comparison, a much larger proportion of CD4 and CD8 T cells stimulated with anti-CD3 mAb divided and although the percentage of CD4 and CD8 T cells that produced IFN-gamma at 4 h was similar to that of gammadeltaT cells, by 72 h the majority of CD4 and CD8 T cells were IFN-gamma(+). Addition of IL-2 did not increase the proportion of gammadeltaT cells that responded to anti-CD3 stimulation by cell division. To test the hypothesis that gammadeltaT cells were inhibited from responding by other mononuclear cell populations within PBMC, monocytes were removed from the PBMC or gammadeltaT cells were purified by magnetic-bead sorting. Only a small distinct population of the sorted cells underwent multiple cell divisions in response to anti-CD3 mAb and removal of monocytes resulted in only a moderate increase in gammadeltaT cell replication. The anti-CD3 mAb stimulation system may provide a useful system to evaluate the difference in the requirements for activation and clonal expansion for gammadeltaT cells versus ab T cells. (C) 2002 Elsevier Science BN All rights reserved.