Activation-induced expression of CD1d antigen on mature T cells

In the present study, we investigated the expression of human CD1d antigen on activated mature T cells. Expression of this glycoprotein Tvas found to be highly regulated and dependent on PHA stimulation. Flow cytometry studie s using the NOR3.2 antibody, which recognized CD1d under denaturing conditi ons, showed a clear increase in its expression after PHA stimulation. Expre ssion of this molecule after PHA activation Tvas confirmed by analysis of i ts corresponding transcript by RT-PCR. A single band representing mRNA for CD1d membrane isoform was observed in activated PBMC as well as in ER3 CD1D -transfected and MOLT-4, pre-T cell lines, which were used as controls. Wes tern blot analysis revealed an activation-dependent increase in CD1d protei n expression when PBMC and enriched T cells were activated for different ti me periods. Activation-dependent expression of CD1d antigen was also confir med in allogenic-activated T cells, suggesting that this event could have b iological significance, Finally, immunocytochemical studies showed the pres ence of this protein at the plasma membrane accompanied by a cytoplasmic an d perinuclear distribution. Results presented herein provide the first expe rimental evidence showing that CD1d antigen is present on circulating, acti vated T lymphocytes, suggesting that its expression is dependent on the act ivation state of the cells. Elucidation of the molecular mechanisms implica ted in the activation-dependent expression of this nonclassical antigen wil l provide new insights into the understanding of antigen presentation and i mmune regulation.