Studies on the Immune Response in Chickens II. Functions of Carrier-Reactive Cells in Anti-Hapten Responses

Roles of T cells in the responses of B cells and B memory cells in chickens were studied using hapten-conjugated carrier antigens. The secondary anti-DNP antibody response to DNP-BSA was generated not only in chickens primed with DNP-BSA but also in those primed with the same hapten on a heterologous carrier such as DNP-BGG and DNP-KLH. Similarly, the secondary anti-DNP response to DNP-BGG occurred in chickens primed with DNP-BSA as well as in those primed with DNP-BGG. Passive administration of anti-DNP antibody did not enhance anti-DNP response to DNP on a heterologous carrier. It is likely, therefore, that carrier-primed cells are not necessary for elicitation of the secondary anti-DNP response, indicating that the carrier effect is not seen in chickens. When chickens primed with DNP-BGG were challenged by DNP-BSA, it was found that DNP-specific memory was generated within a week after priming and maintained longer than for 4 weeks. Moreover, the primary and secondary anti-DNP antibody responses to DNP-BSA of chickens were suppressed markedly by injection of BSA alone. The carrier-induced suppression of anti-hapten response was carrier-specific. The suppressive effect of BSA could be seen in the wide range of doses injected (0.1 to 1 000 mg) and was found to have no relation to immunological tolerance to BSA. The suppressive effect of BSA was exhibited when BSA was injected in the period of from 3 weeks before to 2 days after the challenge by DNP-BSA. Passive administration of anti-BSA antibody could not substitute for the stimulation by BSA in suppressing anti-DNP response to DNP-BSA. It is suggested therefore that the formation of the carrier-specific suppressor cells (T cell) can be activated by injection of carrier alone and results in suppression of anti-hapten response to the hapten on the homologous carrier. From the present study, it has been concluded that helper T memory cells do not seem to play significant roles in generation of the secondary anti-hapten response, and that stimulation by carrier alone is capable of generating the carrier-specific suppressor T cells which act to suppress antihapten response to the hapten on the homologous carrier.