Studies on C3ahu Binding to Human Eosinophils: Characterization of Binding

Abstract

C3a purified to chemical homogeneity from human serum binds preferentially to human eosinophils > neutrophils. Little or no binding is found with human platelets. Maximum binding to eosinophils at 37 °C occurs within 15 min. Dilution of ¹²⁵I-C3a by either cold C3a or washing away unbound ¹²⁵I-C3a and reincubating at 37 °C reveals a T_½ of ∼30 min. C3a_desArg 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.