Preferential Expression of Anti-Azobenzenearsonate Antibodies of Heterozygous a1a3 Rabbits in the a1 Allotype

The preferential expression of anti-As antibodies in the allotype a1 of heterozygous a 1 a 3 rabbits immunized with As-TMA-BSA has been investigated by means of quantitative methods. The average content of the anti-As antibodies in a1 and a3 allotypes was 84 and 11%, respectively; the analogous values for anti-TMA antibodies were 41 and 56%, and for anti-BSA antibodies they were 54 and 41%. The molar anti-As/anti-TMA ratios in the heterozygous animals were approximately the same as in homozygous a 1 a 1 rabbits sensitized with As-TMA-BSA. The very low yields of anti-As-antibodies of allotype a3 cannot be caused by a lack of genes for the production of anti-As antibodies of allotype a3 because a 3 a 3 homozygotes produce considerable amounts of anti-As antibody of allotype a3. Competition between lymphoid cells having anti-As receptors of different allotype and different affinity for the antigenic p-azobenzenearsonate determinant is discussed as a possible cause for the preferential expression in the a1 allotype.