title: Perinatal aspects of immunomodulation.
abstract: Haemopoietic stem cells migrate to liver, bone marrow and thymus, initially from the yolk sac endoderm, by the 28 mm embryo stage. B-lymphocytes differentiate from stem cells, first in the liver and later in bone marrow, becoming pre-B-cells, with cytoplasmic, but no surface, IgM, and later 'baby' B-cells, which carry surface IgM. These last cells are particularly sensitive to the induction of tolerance. Identifiable pre-T-lymphocytes migrate to the thymus, where they acquire the ability to recognize self-antigens coded by the major histocompatibility complex. Models of the generation of idiotype diversity will be discussed with reference to the known characteristics of cells which are differentiating at appropriate tissue sites in the foetus. Functional studies of both maternal and foetal lymphocytes have shown the presence of suppressor lymphocyte activity, from 14 weeks gestation in the foetus to one year in the infant, and during pregnancy in mothers. Infants who have been given blood transfusions, either in utero or in early neonatal life may show prolonged chimerism. Pregnant women may be chimeric for foetal cells and these cells may persist for long periods in the maternal lymphoid system. Antigens reaching the foetus from the mother are capable of modulating immune responses in the offspring. The implications of these and other observations will be discussed, together with the modulation of foetal immune responsiveness and the potential application of techniques designed to direct both antigen unresponsiveness in the newborn and the generation of idiotype diversity.
mesh_terms: D000818:Animals; D001402:B-Lymphocytes / Q000166:cytology; D001665:Binding Sites; D016026:Bone Marrow Transplantation; D002454:Cell Differentiation; D003593:Cytoplasm / Q000276:immunology; D005260:Female; D006801:Humans; D007108:Immune Tolerance; D007111:Immunity, Cellular; D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D007231:Infant, Newborn; D008221:Lymphoid Tissue / Q000166:cytology*; D008431:Maternal-Fetal Exchange; D051379:Mice; D011247:Pregnancy; D011947:Receptors, Antigen, B-Cell; D013601:T-Lymphocytes / Q000166:cytology
chemical_list: D007130:Immunoglobulin Idiotypes; D007075:Immunoglobulin M; D011947:Receptors, Antigen, B-Cell