A product of the C4B locus lacking hemolytic activity

An unusual C4B allotype, C4B 4I, was identified in a study of C4 polymorphism in Japanese. This variant was defined as C4B using a murine monoclonal antibody specific for the C4d region of C4B. Hemolytic assay, however, revealed that the C4 variant, C4 BI was hemolytically inactive in contrast to other well-defined C4B locus products.