Figure 1.

A. C3aR−/− mice and matched controls were injected with K/BxN serum on days 0 and 2, with indistinguishable outcome (n=4 mice per group, representative of 2 experiments). B. Mast cells lying just deep to the synovial lining of a murine tibiotalar joint are identified by toluidine blue staining (left panel) and stain brightly for C5aR in an adjacent section (right panel; inset, isotype). Representative of 4 experiments. C. Instillation of C5a into periarticular tissues of wrist and ankle results in acute edema lacking in mast cell-deficient W^sh mice (n=5 B6 and n=9 W^sh mice pooled from two experiments).