NITRIC-OXIDE SYNTHASE - EXPRESSION OF THE ENDOTHELIAL, CA2+ CALMODULIN-DEPENDENT IN HUMAN B-LYMPHOCYTE AND T-LYMPHOCYTE/

Nitric oxide (NO) is a pleiotropic mediator of a variety of cellular p rocesses such as vasorelaxation, neurotransmission, anti cytotoxicity. We studied the expression of the human endothelial, Ca2+/calmodulin-d ependent NO synthase (NOS) isoform (ccNOS) in highly purified human ly mphocytes from peripheral blood and tonsillar tissue. ecNOS mRNA was d etected in IgD(-) or IgD(-) B cells. peripheral blood and tonsillar ce lls. Upon stimulation. ecNOS mRNA expression decreased in all these ly mphocyte subpopulations. Germinal center T cells and follicular dendri tic cells did not express ecNOS mRNA either in an unstimulated or in a stimulated state. ecNOS expression by human lymphocytes was further s ubstantiated by its mRNA detection in lymphoid cell lines such as Raji , Daudi, and Jurkat. By the use of a specific monoclonal antibody, ecN OS was shown to be present in T cells front peripheral blood and in va rious germinal center cells of frozen tonsillar sections. These data a re the first to demonstrate the expression of the endothelial ccNOS at mRNA and protein level in human lymphocytes.