Defining the RCCX modular structure using different genomic RFLP Southern blot analyses. A, Restriction patterns of TaqI RFLP for the five selected individuals on simultaneous hybridization of probes specific for 3′ RP, CYP21, and 3′ TNX. B, PshAI RFLP hybridized to a 3′ RP probe. C, BamHI RFLP hybridized to a 3′ TNX probe. D, Phenotyping of C4A and C4B proteins by immunofixation of EDTA-blood plasma resolved by HVAGE. E, Immunoblot analysis of Rg1 and Ch1 antigenic determinants in plasma C4 proteins after HVAGE. F, Genomic Southern blot analysis of C4A and C4B genes by PshAI-RFLP (using Probe D) and by PshAI-PvuII RFLP (using probe 22–25). G, HLA class I and class II alleles of the five subjects.