Rabbits of allotype a1a3 were immunized with one of three acidic hapten-bovine serum albumin (BSA) conjugates: p-azophenyl arsonate (AA)-, p-azophenyl sulfonate (SA)-, or p-azobenzoate (CA)-BSA; all animals also received the basic conjugate, p-azophenyl-N-trimethyl-ammonium (TMA)-BSA. After 6 to 12 months, each animal was challenged with the same combination of BSA conjugates as given originally. The allotype of the plaque-forming cells (PFC) from lymph nodes and spleen was determined by enhancement with anti-allotype antisera. PFC detected upon addition of anti-a1 were designated a1-PFC and those detected with anti-a3 were designated a3-PFC. Results were expressed as the ratio of a1-PFC to a3-PFC. For the basic hapten, TMA, this ratio was 0.2 to 1.0 for nine lymph nodes and 0.3 to 1.6 for seven spleens. In contrast, the ratio for the acidic haptens was much higher: for AA, from 4 to 16 in three lymph nodes and 24 to 87 in two spleens; for SA, from 4 to 114 in three nodes and 38 to 59 in two spleens; for CA from 13 to 130 in two nodes and 4 to 33 in three spleens. Analogous use of anti-allotype sera for enhancement of anti-acidic hapten hemolytic serum titers showed that anti-a1 gave 8 to 16 times the enhancement given with anti-a3. Thus, the results indicate that the a1a3 rabbits made little or no antibody of allotype a3 during the secondary response to these acid haptens.

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This work was supported in part by Research Grant AI 06057 from The National Institutes of Health, Bethesda, Maryland.

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