[Expression of T-lymphocyte antigens by serum B lymphocytes in rheumatoid polyarthritis].

Molecules recognised by the monoclonal antibodies Leu 1 - OKT 1 - Mid 5 (CD5 molecules) were originally shown on human T cells and are equivalent to Lyt-1 molecules in the mouse. These surface molecules are detectable on some human B cells, but are weakly expressed. We have therefore tested the effects of the tumour-promoter, phorbol myristic acetate (PMA) on expression of these molecules on B cells. Sheep red blood cell rosette-depleted lymphoid organ or blood cells from 8 controls and 10 rheumatoid arthritis (RA) patients were examined fresh and cultured with PMA for 48 hours and the cells stained with Leu 1 or Mid 5 by indirect immunofluorescence. Cells were analysed by UV microscopy or flow cytometry. More RA blood B cells were positive for Leu 1 than normals before culture. Following incubation with PMA, the percentage of positive cells increased in all cell populations (1-49% in RA patients and 5-26% in controls). There was no difference in the expression of Leu 1 on Kappa--or lambda--positive cells before and after culture in PMA. Leu 1 positive cells were under-represented in Epstein-Barr virus-driven cell lines.