The termination of immunological unresponsiveness to bovine serum albumin in rabbits. I. Quantitative and qualitative response to cross-reacting albumins.

Rabbits made unresponsive to BSA at birth were given two courses of immunization with various cross-reacting albumins at 3 months of age. Normal control rabbits, of equivalent age and weight, were similarly immunized. Sera obtained 7 days after the last injection were assayed for binding and precipitating antibody to six albumins and for their avidity for BSA. No significant differences were found between unresponsive and normal rabbits in the amount of antibody reacting with any of the six albumins used. This was the case regardless which albumin was used to terminate the unresponsive state. Avidity differences were seen and seemed to depend on the antigen used and not on the immunological status of the animal. The simultaneous injection of small amounts of BSA inhibited the termination of unresponsiveness. These results were discussed in the light of the more recent theories of the termination of unresponsiveness and of antibody formation.