The influence of naturally occurring suppressor cells of systemic graft versus host reaction (GvHR in fetal and newborn mice.

The early symptom (splenomegaly on day 7) of a graft versus host reaction (GvHR), induced in F1 fetal and newborn mice on day 0 or +1 after birth, is significantly reduced as a result of action of suppressor cells in comparison with 3-day-old recipients. However, late symptoms of GvHR, measured by a body-weight-gain assay and mortality, are similar in the recipients injected with parental spleen cells either on day 0 or +3. An existence of contra suppressive factor(s) operating in newborn early after birth is suggested.