Birgitta Heyman

Immunoglobulin-Secreting Cells of Maternal Origin Can Be Detected in B Cell-Deficient Mice

Abstract It is well known that the transfer of immunoglobulins (Igs) from mother to young via milk contributes to the offsprings 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 (μ−/−) mice and found that a high proportion of them obtain long-lasting, partial reconstitution of their serum Ig levels if born to μ+/− mothers. In some of these serum IgG-positive μ−/− mice, Ig-secreting cells were detected in spleen and bone marrow. To ensure that cells of maternal origin were present in the progeny, μ−/− offspring born to μ+/− dams transgenic for green fluorescent protein (GFP) were used. In spleens and bone marrow from some of these μ−/−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 μ−/− mice that were born to μ−/− dams and transferred to a lactating μ+/+ foster dam at birth. This indicates that maternal Ig-secreting cells can be transferred postnatally via milk.

Immune complex-mediated enhancement of antibody responses without induction of delayed-type hypersensitivity.

Immunoglobulin (Ig)G and IgE antibodies enhance the humoral response in vivo to soluble antigens with which they form complexes. In vitro, antigen is targeted to B cells by IgE antibodies and to macrophages and dendritic cells (DCs) by IgG, thus leading to increased antigen presentation to specific T cells. Possibly these mechanisms are also responsible for antibody‐mediated enhancement in vivo. We now address the question of whether IgG‐ and/or IgE‐antigen complexes can prime for delayed‐type hypersensitivity (DTH), a reaction known to require primed T helper (Th)1 cells. Mice were immunized with IgG‐anti‐2,4,6‐trinitrophenyl (TNP)/BSA‐TNP or IgE‐anti‐TNP/BSA‐TNP. Mice given BSA‐TNP alone or BSA‐TNP in complete Freunds adjuvans (CFA) were used as controls. DTH and IgG‐anti‐BSA levels were measured after subsequent challenge with BSA. A potent BSA‐specific antibody response was induced by IgE‐ or IgG‐complexed antigen as well as by CFA/antigen but DTH‐reactions were only observed in mice immunized with CFA/antigen. Both IgE and IgG enhanced the production of BSA‐specific IgG1, IgG2a and IgG2b, although the most pronounced enhancement was seen in the production of IgG1. These findings suggest that Th2 cells rather than Th1 cells are involved in the immune response to IgG‐ and IgE‐immune complexes.