Cells expressing dendritic cell markers are present in the rheumatoid nodule

Objective, To determine if dendritic antigen-presenting cells (DC) are pres ent in rheumatoid nodules, as has been reported in the synovial lesions of rheumatoid arthritis. Methods. Nodules (n = 14) were examined with monoclonal antibodies (Mab) re cognizing the DC differentiation/activation markers CD83, CMRF44, and CMRF5 6 and an antibody recognizing the CD1a antigen present on epithelial tissue associated DC. Results. Cells expressing CMRF44 were common in rheumatoid nodules, compris ing 22% of nucleated cells versus 13% in synovial membranes (n = 10). Cells positive for CD1a (5%) and CD83 (2%) were less common. A majority (86%) of CMRF44 positive cells,were also positive for the macrophage marker CD14. T his left a significant minority of putative DC that were single stained wit h CMRF44. Conclusion. Cells bearing DC markers are as frequent in the rheumatoid nodu le as in the synovial lesions. A majority are "indeterminate" cells that ar e CD14 positive but a proportion are single stained putative DC. The lack o f lymphoid collections containing DC and T and B lymphocytes in the nodule suggests that local presentation of antigen may not occur in the rheumatoid nodule, as is thought to be the case in synovial membranes containing lymp hoid follicles, This difference could potentially be explained by different states of activation, and differentiation of DC within the 2 lesions.