Immunological and immunohistochemical analysis of rheumatoid nodules.

An attempt was made to examine the pathophysiology of the rheumatoid nodule. Significant amounts of interleukin 1-like activity and prostaglandin E2 were detected in the supernatants from in vitro organ cultures of rheumatoid nodule tissue. When fresh (but not old) rheumatoid nodules were minced and cultured in vitro prominent outgrowths of cells were observed. These cells expressed both HLA-DR and CD14 antigens but lacked conventional differentiation antigens for T cells and B cells, suggesting that they are of monocyte-macrophage origin. These data suggest that interleukin 1 and prostaglandin E2 may be deeply involved in the formation of rheumatoid nodules.