Formation of leukocyte inclusions in normal polymorphonuclear cells incubated with synovial fluid

Normal polymorphonuclear cells phagocytosed IgG, IgM and β 1c (C3)‐containing inclusions from the majority of rheumatoid factor‐positive synovial f.uids, but not from factor‐negative fluids, as determined by fluorescent antibody staining. Addition of rheumatoid factor (but not Waldenström IgM) to factor‐negative rheumatoid fluids produced phagocytosable complexes of similar composition in these fluids, indicating the presence of altered IgG in factor‐negative as well as factor‐positive rheumatoid effusions. Inclusions were infrequently phagocytosed from nonrheumatoid effusions.