The ability to distinguish immunoglobulin (Ig) of paternal allotype both on lymphocyte membranes and in the serum of neonatal b4b5 heterozygous rabbits has allowed us to study the postnatal ontogeny of cells bearing endogenously synthesized Ig that could not have been derived from the mother. In normal b4b5 rabbits, such endogenously synthesized Ig of paternal allotype is present on the membranes of bone marrow-derived (B) lymphocytes from birth, but does not appear as detectable circulating Ig until ∼2 wk of age.
In the neonate, cells bearing the paternal allotype are potential targets for the induction of chronic allotype suppression. Within 24 h of exposure to anti-allotype antisera in vivo, Ig of the suppressed paternal allotype is no longer detectable on the surface of neonatal lymphoid cells. Further, this lymphocyte membrane Ig is eliminated and not simply masked by the suppressing antibodies. Finally, cells bearing the suppressed allotype are deleted from all lymphoid organs for the duration of total allotype suppression, and reappear first in bone marrow and peripheral blood at the time of spontaneous escape from suppression.