Decrease in HLA-DR-positive monocytes in patients with systemic lupus erythematosus (SLE).

Monocyte populations expressing HLA-DR antigens were studied in SLE patients by flow cytofluorometry with indirect immunofluorescence. Both the number of HLA-DR-positive monocytes and the expression of HLA-DR antigens on monocytes were markedly decreased in active SLE patients and were recovered to the normal level in inactive SLE patients. Because Ia-positive monocytes play a regulatory role for several immune responses, the decrease in HLA-DR-positive monocytes will result in abnormal regulations of immune responses and will play some critical role in the pathogenesis and the process of SLE.