HLA-D region products are expressed in endothelial cells.

The mixed lymphocyte endothelial cell culture was studied by the primed lymphocyte typing (PLT) technique. By comparing the HLA-D/DR specificity of the secondary response when using either peripheral blood mononuclear cells (PBM) or endothelial cells from umbilical cords for priming or restimulation of lymphocytes, it was found that PBM from newborn would induce a clear-cut specificity for HLA-D/DR when used for priming a well a for restimulation. No HLA-D/DR specificity was seen, however, when endothelial cells were used for restimulation of lymphocytes primed to HLA-D/DR on PBM. On the other hand, lymphocytes primed to endothelial cells showed significant, albeit not very strong specificity for HLA-D/DR when restimulated with PBM. Our experiments suggest that HLA-D region products are present on endotheial cells, and thus confirm and extend serological studies using anti DR antisera.