Ontogeny of mouse B lymphocytes and inactivation by antigen of early B lymphocytes

Taking advantage of recent findings about membrane fluidity, the authors studied and compared the biosynthetic capacities of fetal or neonatal mouse B (bone marrow derived) lymphocytes (until 10 days after birth) and adult B lymphocytes. Although both early and adult lymphocytes can synthesize surface immunoglobulins, they have a different physiological behavior after interaction with a ligand (anti immunoglobulin sera or antigen), either in vivo or in vitro. Fetal and neonatal lymphocytes bearing surface immunoglobulins do not reexpress their membrane receptors after capping and endocytosis promoted by anti immunoglobulin sera. On the other hand, adult lymphocytes resynthesize completely their receptors after the same treatment. Furthermore, intrafetal injections of hemocyanin in pregnant mice lead to a striking decrease in the number of hemocyanin binding cells. It seems plausible that this non reexpression of surface immunoglobulins could be the first step in tolerance establishment.