title: Cellular mechanisms of restricted immunoglobulin formation in the human neonate.
abstract: The functional capacity of human neonatal B lymphocytes has been investigated by in vitro methods using T lymphocyte-dependent (pokeweek mitogen, PWM) and -independent (Epstein-Barr virus, EBV) polyclonal B cell activators. B cell activation of single cells was detected by class-specific immunoglobulin (Ig) secretion using a reversed hemolytic plaque assay. It was found that neonatal B cells were triggered to secretion of IgM by EBV, with a magnitude comparable to adult levels, but that, in contrast to B cells from adults, they did not secret IgG. Cord lymphocytes did not secret Ig although they displayed a sizable DNA synthetic response to PWM. Using cell separation and culture experiments, it was shown that (allogeneic) adult T lymphocytes could restore cord B cell responsiveness to PWM and that cord T lymphocytes could not cooperate with adult B cells. In addition to this immaturity of cord T helper function for antibody synthesis, we found cells in the cord T cell-enriched fraction which inhibited the polyclonal response of adult lymphocytes to both PWM and EBV. These lymphocytes suppressed adult B lymphocytes directly but appeared ineffective against neonatal B lymphocytes themselves. The nature of these suppressing cells and their possible role in the fetal/maternal relationship are a matter of speculation.
mesh_terms: D000921:Antibody-Producing Cells / Q000378:metabolism; D001402:B-Lymphocytes; D002469:Cell Separation; D004247:DNA / Q000096:biosynthesis; D005260:Female; D005312:Fetal Blood / Q000166:cytology; D004854:Herpesvirus 4, Human / Q000276:immunology; D006801:Humans; D007111:Immunity, Cellular; D007136:Immunoglobulins / Q000096:biosynthesis*; D007231:Infant, Newborn; D008213:Lymphocyte Activation; D011043:Pokeweed Mitogens / Q000494:pharmacology; D011947:Receptors, Antigen, B-Cell / Q000145:classification; D013601:T-Lymphocytes
chemical_list: D007136:Immunoglobulins; D011043:Pokeweed Mitogens; D011947:Receptors, Antigen, B-Cell; D004247:DNA