Phenotypic markers of lymphocyte and mononuclear phagocyte activation within rheumatoid nodules

We investigated rheumatoid subcutaneous nodules using monoclonal antibodies recognizing functional determinants on mononuclear phagocytes (Mph) and lymphocytes. Mph at the center of rheumatoid nodules showed strong expression of the leukocyte integrins CR3 and p150,95 which would be consistent with the presence of a central chemotactic stimulus. Mph expression of FcR1, a gamma interferon regulated molecule, was decreased in 5/13 cases despite strong expression of MHC class II. There was a variable unstructured infiltrate of T lymphocytes, a majority of which were CD8 positive. Lymphocytes showed increased MHC class II expression but interleukin 2 receptor expression was low. We discerned no relationship between the number, distribution or phenotype of the T cell infiltrate and the phenotype of the predominant Mph population.