| Research Abstract |
Fas (APO-1/CD95) is a membrane-associated molecule that mediates apoptosis and may play a role in the induction and maintenance of T cell self-tolerance. To elucidate the involvement of Fas in systemic lupus erythematosus (SLE), Fas expression by peripheral blood mononuclear cells (PBMC) from patients with SLE,rheumatoid arthritis (RA) and from healthy donors was analyzed, using three-color flow cytometry and semiquantitative RT-PCR.Several new findings were obtained as follows ;
(a) A significant expression of Fas was observed in CD45RO^- naive T cells from SLE patients. CD4^+CD45RO^- T cells from SLE patients co-expressed Fas and early to intermediate activation antigens such as CD25 and CD71. Mean fluorescence intensity of Fas on CD4^+ T cell subsets inversely correlates with the absolute size of CD4^+ T cell subsets in peripheral blood of SLE patients. There results suggest that T cells with invreased Fas expression may be highly susceptible to apoptosis, in vivo.
(b) Exon 6-deleted
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Fas cDNA encoding soluble form of Fas protein (sFas) was isolated from PBMC of SLE patients and was generated by alternative splicing, exon skipping.
(c) Gene expression of sFas and mFas by PBMC from SLE patients and healthy donors was examined by a semiquantitative RT-PCR method. PBMC from healthy donors expressed a constant proportion of sFas to mFas mRNA,while those from SLE patients did a greatly variable level of sFas and mFas. This result indicates that gene expression of Fas by PBMC from SLE patients is dysregulated.
(d) Serum levels of sFas were measured by a newly developed sandwich ELISA.Serum from SLE,especially active, showed a significant increase in both the level and positivity of sFas compared to healthy donors and other autoimmune diseases, including RA,PSS,DM/PM,and primary SS.
(e) sFas mRNA was also identified in the liver of WKA and LEC rats, indicating that sFas molecule may play a role in regulating apoptosis in mammalian immune responses, such as activation-induced cell death. Less
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