MONITORING OF CD95 (APO-1 FAS) LIGAND EXPRESSION IN HUMAN T-CELLS BY QUANTITATIVE RT-PCR/

CD95 (APO-1/Fas) receptor/ligand interaction is a key regulatory pathw ay for apoptosis in lymphoid cells. We developed a quantitative RT-PCR for the human CD95-L to determine expression levels in lymphoid cell lines and in lymphocytes derived from blood of healthy individuals. In untreated peripheral blood T lymphocytes and T cell lines constitutiv e expression of the CD95-L mRNA was found at low levels. Stimulation o f T cells by treatment with PMA and ionomycine (P/I) lead up to a 100- fold maximal increase in CD95-L mRNA after 4 h. CD95-L mRNA is produce d by activated CD8 and CD4 T cells. In vivo increased CD95-L mRNA expr ession was found in freshly isolated T cells during the acute phase of EBV infection. In contrast to T cells, CD95-L mRNA could be induced i n some B lineage cell lines only after five days of stimulation. Since defective or accelerated CD95/CD95-L interaction is considered to be involved in the pathogenesis of lymphoproliferation, autoimmunity and AIDS, the quantitative RT-PCR assay described in this paper may provid e a powerful tool for monitoring CD95-L expression in these diseases.