diet enriched in vitamin A acetate or in vivo administration of interleukin-2 can counteract a tolerogenic stimulus

A conventional diet enriched in retinyl acetate (vitam in A a ce tate; VAA) or in vivo administration of exogenous interleukin-2 (IL-2) can effectively annul the otherwise tolerogenic stimulus represented by (CBA x C57BL /10ScSn) F1 cells injected intraperitoneally into newborn CBA mice. On the basis of these data and results of others, we postulate that an antigenic stim ulus associated with a relative lack of IL-2 (or generally the lack of a ‘secondary stimulus’) can be tolerogenic rather than immunogenic. However, the tolerogenicity of the antigenic stimulus can be substantially reduced or even converted to sensitization (R. P. Cleveland & H. N. Claman, J. lmmun. 124, 474- 480, 1980), when the antigenic signal is appropriately associated with a concomitant or additional stimulus possibly mediated through IL-2.