Figure 2.

Polymorphic variants, RCCX modules and gene copy number variations of human complement C4B and C4A - from phenotypes to genotypes. (A) Polymorphisms of C4 protein. EDTA-plasma from 15 human subjects were treated with neuraminidase and carboxypeptidase B, subjected to high voltage agarose gel electrophoresis to resolve C4 plasma proteins based on gross differences in electric charge, immunofixed with goat antiserum against human C4, blotted to remove diffusible proteins and then stained. The most common form of C4 allotypes are B1 and A3 (red fonts). The left of panel (A) showed common variants of C4B. The right of panel (A) showed common variants of C4A. Band intensities in each lane reflected the relative expression levels of various protein allotypes. (B) TaqI restriction fragment length polymorphism (RFLP) of DNA samples from the same subjects to demonstrate RCCX modular variations. (C) PshAI-PvuII RFLP to elucidate the relative dosage of C4B and C4A genes. Please refer to of Figure 1F for interpretation of long and short C4 genes in linkage with RP1 or RP2. Definitive assignments of C4A and C4B protein allotypes in each subject often require parallel genotyping experiments to determine RCCX modular variations and C4A and C4B gene copy numbers as shown here.