Cellular Origin of Rheumatoid Factor

The rheumatoid factor, a group of unusual macroglobulins, is demonstrable in the serum of the majori ty of patients with rheumatoid arthritis and in a relatively small proportion of patients with other diseases (1). The presence of this factor can be demonstrated by its reaction with human v-globulin (Cohn fraction I I ) in such serological procedures as the tanned sheep cell agglutination (2) and latex fixation tests (3), as well as by precipitin tests (4). The reactive component of "y-globulin seems to be an aggregate (5) with high sedimentation coefficients, which forms an insoluble complex with the rheumatoid factor. The origin and site of production of the rheumatoid factor has been unknown. In the present study, fluorescein-labelled aggregated human 7-globulin was used as a specific reagent for its detection in situ. The results show that the factor is present in certain cells of the synovial tissues, lymph nodes, and subcutaneous nodules in active rheumatoid arthritis.