Studies on the development of the isoantigens of the H-2 system in newborn mice.

Summary 1.Erythrocytes and spleen cells from C3H mice were insensitive to humoral H-2-isoantibodies until 2–3 days after birth. Adult reactivity was reached after 6–10 days. 2.Newborn, less than 1 ½-day-old C3H mice were able to absorb intravenously injected antiserum. 3.Erythrocytes of less than 1 ½-day-old C3H mice could not absorb H-2-isoantibodies in vitro . 4.Spleen, liver and kidney cells of less than 1 ½-day-old C3H mice were able to absorb isoantibodies in vitro . 5.Erythrocytes and spleen cells of newborn CBA and A mice were insensitive to humoral isoantibodies at 1 ½ days after birth. 6.Erythrocytes and spleen cells of newborn C57B1 and C57L mice were sensitive to humoral isoantibodies from the day of birth. 7.Immunization of adult C57L mice with x-irradiated spleen cells of less than 1 ½ day old C3H mice gave rise to humoral antibodies.The possible significance of these findings is discussed.