Mouse amniotic fluid (MAF) and neonate sera (NNS) will be fractionated by physical and chemical techniques in an attempt to isolate and characterize the neonatal immune suppressive factor(s) present in these fluids. The mechanism of suppression by MAF, NNS and suppressor(s) isolated from them, including AFP, will be explored. Experiments will focus on the question of the role of the macrophage in suppression and whether the development of suppressor cells is induced by these factors. Further studies of the genetic restriction in suppression by MAF will be undertaken using cloned alloreactive T cells with specificities for various MHC and non-MHC loci. The in vivo effect of MAF on adult animals will be investigated on the following: 1) delayed hypersensitivity; 2) skin graft rejection; 3) immunological tolerance; 4) the antibody response to T dependent and independent antigens; and 5) the induction of suppressor cells. We will continue our studies on the immune response in pregnancy, particularly the role of nonspecific suppressor cells for antibody synthesis in the spleens of pregnant mice and the production of paternal antigen specific suppressor cells in the draining lymph nodes (DLN) of the uterus. Cloned alloreactive T-cells specific for F1 hybrid antigens will be used to detect such antigens in the DLN of allogeneic pregnancies. Maternal cells responding to and/or suppressing the response to F1 antigens will be sought in DLN. The presence of antigen specific blocking factors in the sera of pregnant animals for paternal and F1 determinants and their production by DLN and/or other lymphoid tissues will be explored.