Complement-inhibiting and anti-inflammatory properties of chlorazole fast pink 2BL

Chlorazole fast pink 2BL inhibited the classical complement pathway in rat serum both in vivo and in vitro. The in vitro potency of chlorazole fast pink against the alternative pathway could not be assessed accurately but it was clearly less than that against the classical pathway. The compound appears to bind strongly to albumin with a resulting decrease in potency in undiluted as compared to diluted serum. Anti-inflammatory activity was observed in models of inflammation known to be highly complement-dependent (direct passive Arthus, zymosan oedema) but not in models in which complement is not involved (dextran oedema) or plays a minor role (carrageenan oedema).