Neonatal splenic suppressor cells in the chicken. I. In vivo suppression of the immune response to bovine serum albumin by normal and tolerized neonatal spleen cells.

The presence of active splenic suppressor cells in neonatal chickens, either normal or tolerant to bovine serum albumin (BSA), was examined by assessment of their effect on both primary and adoptively transferred secondary responses to BSA or sheep red blood cells (SRC). Both normal and BSA tolerized spleen cells were shown to be highly suppressive of secondary anti-BSA responses generated by specifically primed adult spleen cells in inert recipients. Suppression of the secondary anti-BSA response by normal spleen cells was slightly less effective than that seen with BSA tolerant spleen cells. Transfer of BSA tolerant spleen cells into normal recipients, followed by BSA challenge, prevented any significant primary anti-BSA response. In contrast, transfer of normal spleen cells into normal recipients, followed by BSA challenge, failed to show any suppression of the resulting primary response. Neither normal nor BSA tolerant neonatal spleen cells were capable of suppressing either primary or secondary responses to SRC. Thus, chickens tolerized to BSA have suppressor cells specific for the tolerizing antigen. We present evidence that both the tolerance associated suppressors and the suppressors detected in normal neonatal chickens are T cells.