Decreased CD161+CD8+ T cells in the peripheral blood of patients suffering from rheumatic diseases

Abstract

Objectives. Although it has been reported that the numbers of both CD4 CD8 and CD4 natural killer T (NKT) cells are selectively decreased in the peripheral blood of patients with rheumatic diseases, there have been no reports concerning a novel subpopulation of CD8 NKT cells. To examine whether CD161 CD8 T cells, which are closely related to CD8 NKT cells, are also decreased in patients with rheumatic diseases, we have investigated the expression of CD161, together with that of CD28, CD25 and CD62L, on T cells in the peripheral blood of these patients. Methods. The rheumatic diseases evaluated in this study were systemic lupus erythematosus (SLE) (n 54), mixed connectivetissue disease (MCTD) (n 15), systemic sclerosis (SSc) (n 14), polymyositis/dermatomyositis (PM/DM) (n 13) and rheumatoid arthritis (RA) (n 24). Healthy donors were examined as controls (n 18). The expression of CD161, CD28, CD25 and CD62L on T cells was analysed by flow cytometry. Results. Both the frequency of CD161 expression on CD8 cells and the absolute number of CD161 CD8 cells were significantly decreased in patients with SLE, MCTD, SSc and PM/DM. Only the absolute number of CD161 CD8 T cells was significantly decreased in RA. CD161 expression on CD28 CD8 T cells was significantly decreased in SLE, MCTD and SSc. The absolute number of CD161 CD8 CD62L T cells was significantly decreased in SLE, MCTD and SSc. Conclusions. Both the frequency and the absolute number of CD161 CD8 T cells were decreased in the peripheral blood of patients suffering from SLE, MCTD, SSc and PM/DM. This result suggests that there is also an abnormality of NKT cells in the CD8 population.