Role of I-J in neonatal suppression.

Spleen cells from neonatal mice belonging to strains with the I-J-b or I-J-k genotype, were treated with anti-I-Jb or anti-I-Jk antibody and complement. This reduces their suppressor cell activity as demonstrated by a decrease in the ability to suppress the mixed-lymphocyte reactivity of adult spleen cells. Injection of anti-I-J antibody into neonatal mice also reduces splenic suppressor cell activity prematurely. The removal of suppressor cells from neonatal spleen does not result in an immediate increase in mixed-lymphocyte reactivity (cell-mediated immunity) but does hasten the development of mixed-lymphocyte reactivity in the young mice. The results are discussed in light of the hypothesis that suppressor cells inhibit the function of immunocompetent cells in the neonatal mouse and control the development of immunocompetence.