The cytology of joint exudates in rheumatoid arthritis. Morphology and preparation techniques.

The cytology of joint exudates from patients with rheumatoid arthritis was examined by preparation of air-dried smears; a procedure that involved cytocentrifugation of synovial fluids following dilution in a balanced salt solution containing albumin. This procedure provided a monolayer of homogeneously distributed exudate cells with excellent preservation of morphological details. The dominant cell type in the exudates was polymorphonuclear leukocytes, often with signs of necrobiosis. The small and medium-sized mononuclear cells were lymphocyte-like and vital-looking. The large mononuclear cells displayed signs of extensive phagocytosis, especially phagocytosis of polymorphonuclear leukocytes. It is suggested that the granulocytes of the synovial fluid are cells which have reached their function compartment, where they work and die.