Immunoglobulin-secreting cells of maternal origin can be detected in B cell-deficient mice

It is well known that the transfer of immunoglobulins (Igs) from mother to young via milk contributes to the offspring's immune defense. The present study suggests that not only is IgG transmitted to progeny, but that functional maternal Ig-secreting cells (or B cells) can also be transferred to the neonate. We have used B cell-deficient (mu (-/-)) mice and found that a high proportion of them obtain long-lasting, partial reconstitution of their serum Ig levels if born to mu (+/-) mothers. In some of these serum IgG-positive mu (-/-) mice, Ig-secreting cells were detected in spleen and bone marrow To ensure that cells of maternal origin were present in the progeny, mu (-/-) offspring born to mu (-/-) dams transgenic for green fluorescent protein (GFP) were used. In spleens and bone marrow from some of these mu (-/-)GFP(-/-) offspring, GFP-positive cells were detected, which demonstrated that cells of maternal origin could infiltrate the progeny. In addition, splenic Ig-secreting cells were detected in mu (-/-) mice that were born to mu (-/-) dams and transferred to a lactating mu (+/+) foster dam at birth. This indicates that maternal Ig-secreting cells can be transferred postnatally via milk.