Evidence for common antigens on human non-adherent synoviocytes (type A) and peripheral monocytes

The characterization of a homogeneous non-adherent synoviocyte (Type A) cell population (greater than or equal to 95%) from non-rheumatoid patients by culturing the cells in the presence of forty percent foetal calf serum is reported. These cells were able to phagocyte latex beads, iron particles, fluoresceinated zymosan and yeast. Furthermore, non-adherent synoviocytes were capable of being infected by the obligate intracellular parasite of peripheral monocytes Leishmania donovani. Indirect immunofluorescence experiments with specific anti-human monocyte (OKM1) antibody and specific antisynoviocyte serum, showed the presence of common surface structures between synoviocytes A cells and peripheral monocytes. Fifty five percent of the synoviocytes were also positive for HLA Dr antiserum. Analysis by two dimensional gel electrophoresis showed that peripheral monocytes and synoviocytes secreted identical polypeptides in vitro. These results strongly suggest a relationship between synoviocytes A and mononuclear phagocyte system.