Studies on C3ahu binding to human eosinophils: characterization of binding.

C3a purified to chemical homogeneity from human serum binds preferentially to human eosinophils greater than neutrophils. Little or no binding is found with human platelets. Maximum binding to eosinophils at 37 degrees C occurs within 15 min. Dilution of 125I-C3a by either cold C3a or washing away unbound 125I-C3a and reincubating at 37 degrees C reveals a T1/2 of approximately 30 min. C3adesArg neither binds to eosinophils nor inhibits the binding of 125I-C3a. The binding of C3a to human eosinophils may reflect a physiologic role of C3a in eosinophil motility or function.