Rheumatoid Arthritis Synovial Dendritic Cells Produce Interleukin-1

Previous studies have identified a non-phagocytic dendritic cell (DC) in the synovium of patients with rheumatoid arthritis (RA). These cells do not bear conventional markers of B cells, T cells or monocytc/macrophages (MO) but do express MHC class II antigen (HLA-DR). They are potent stimulators of allogeneic and autologous mixed lymphocyte reactions and are efficient accessory cells for T-cell responses to mitogen and antigen Here we report that they also produced interleukin-1 (IL-1) activity in vitro and this could be stimulated further with bacterial lipopolysacchandc (LPS). DC supernatants contained no detectable interleukin-2(IL-2) activity. The role of this cell in vivo is unknown but its accessory function and IL-I production suggest that it could contribute to immune and inflammatory-mediated tissue damage in the rheumatoid joint