Phenotypic characterization of cells within subcutaneous rheumatoid nodules.

An immunohistochemical double-staining technique was applied to frozen sections of biopsies from subcutaneous rheumatoid nodules. Material within the central necrosis reacted with anti-immunoglobulin and anti-HLA-DR antibodies. Cells within the palisading layer were "macrophage-like," as indicated by staining for anti-HLA-DR and OKM1, and showed a high proliferative activity as seen by OKT9 reactivity. The granulation zone contained many (alpha Leu-1+) T cells in close contact with HLA-DR-expressing non-T cells.