Contribution of Allelic Genes A b 4 and A b 5 To Formation of Rabbit 7S γ-Globulins. ∗

Abstract

Summary

1. A method for quantitative analysis of allotypes is presented, based on successive precipitations of specific allotype from I¹³¹-labeled 7S γ-globulin with anti-allotype sera. 2. In the homozygotes or heterozygotes, 80–90% of the γ-globulin molecules have Ab4 or Ab5; 10–20% of the γ-globulin molecules have neither Ab4 nor Ab5. 3. An anti-Ab5 serum giving 2 precipitin bands with Ab5 sera was compared with an anti-Ab5 serum giving one precipitin band and was found to precipitate virtually the same quantity of γ-globulin-I¹³¹ (82% vs 80%) from the same γ-globulin preparation. This indicates that the 2 precipitin bands represent cross-reacting antigen-antibody systems. 4. In the heterozygote, 64% of the molecules have Ab4, 27% have Ab5. These quantities are independent of the order of precipitation, indicating that Ab4 and Ab5 are not found on the same γ-globuin molecules but only on separate molecules. The limit of overlap is less than 5%. 5. The question as to why allelic genes do not contribute to the same molecule, although both alleles appear to be operating in the synthesis of γ-globulin within the same cell, is discussed. It is suggested that polypeptide chains carrying the allotypic specificity Ab4 form pairs immediately after synthesis; and that the Ab4 pairs do not combine with similarly formed Ab5 pairs.