T-cell expression of CD91 - a marker of unresponsiveness to anti-TNF therapy in rheumatoid arthritis.

The aim of this study was to investigate the expression of thrombospondin-1 (TSP-1) and its receptors, lipoprotein receptor-related protein/cluster of differentiation (CD)91, calreticulin (CRT), and CD47, on T cells and monocytes from patients with rheumatoid arthritis (RA) treated with anti-tumor necrosis factor (TNF) therapy. The surface expression of CD91 and associated components on CD3- and CD14-positive cells was examined using flow cytometry in 12 patients with established RA before and after beginning therapy and compared with that of 9 healthy controls and 12 patients with early RA treated with conventional therapies. CD3-positive cells from anti-TNF non-responders showed significantly greater expression of CD91 expression than those from responders (p<0.05) after 6 weeks and when all measurements were pooled (p<0.001). CD91 expression on CD3-positive cells from non-responders to other therapies was at the same level as in healthy controls. In contrast, CD14-positive cells showed no differences in CD91 expression between patients and controls or between responders and non-responders to anti-TNF therapy. The expression of TSP-1, CRT, and CD47 showed no differences between responders and non-responders. The results suggest T-lymphocyte expression of CD91 to be a biomarker that signifies unresponsiveness to anti-TNF therapy in patients with RA and may be used to identify potential responders and non-responders.