Figure 2. .

Different genetic mechanisms leading to lower expression of C4A protein than of C4B protein in four families with SLE. In each family, the RCCX modular structures were determined by PFGE of PmeI-digested genomic DNA, Southern blotting, and hybridization to a C4d-specific probe (A). TaqI genomic RFLP was applied to yield details of genomic structures for the RCCX constituents, including the dichotomies of RP1 and RP2, C4 long and C4 short linked to RP1 or RP2, CYP21B, CYP21A, TNXB, and TNXA (B). PshAI-PvuII RFLP was applied to determine the relative GCNs of C4A and C4B (C). The C4A and C4B protein polymorphisms were elucidated by immunofixation of EDTA plasma resolved by high-voltage agarose-gel electrophoresis (D). P = patient; M = mother; F = father; S = sibling (S1 = sibling 1; S2 = sibling 2).