Location and phenotype of putative dendritic cells (DCs) and macrophages in inflamed tissue. Frozen sections prepared from a block of inflamed tissue containing synovium are shown. Tissue was obtained from the lateral side of the ankle 9 days after adoptive transfer of arthritis. (a) Frozen section showing inflamed synovial lining (arrow), subintimal connective tissue (CT), and tendon (T), stained with hematoxylin and eosin. (b) High-power view of area from box in (a) shows polymorphonuclear cells. (c) Indirect immunoperoxidase, isotype-matched control monoclonal antibody (mAb). (d) Section stained with mAb OX1 showing dense infiltration of the synovial lining and subintimal connective tissue with CD45+ cells. (e) Staining with mAb OX6 shows large number of MHC II+ cells in the synovial lining and subintimal connective tissue. (f) CD163+ cells stained by mAb ED2 are located mainly in the synovial lining as type A synoviocytes and are present in the subintimal connective tissue in small numbers. (g) CD11c+ cells, stained by mAb 8A2, are located mainly in the subintimal connective tissue. (h) High-power view of area from box in (g) shows CD11c+ monocytes (arrowheads) and DC-like cells (arrow and inset). Objectives, × 60. MHC, major histocompatibility complex.