The ability of the murine placenta to absorb monoclonal anti-fetal H-2K antibody from the maternal circulation.

In previous work we have found that partially purified 125I-labeled anti H-2 antibody is localized in the placenta when injected i.v. into females pregnant by males bearing the target haplotype. This led to the concept that the placenta is an H-2 antigen-bearing immunoabsorbent barrier between mother and fetus. In this report we have used an anti-H-2Kk monoclonal antibody of the IgG2a subclass, also labeled with 125I, to verify this concept, as well as to improve the genetic definition of the immunoabsorbent antigen. In addition we have prepared F(ab')2 fragments of this antibody, and these also show the immunoabsorbent effect. This indicates that transport into fetally derived tissues via Fc binding is not a prerequisite for reaction of the antibody with paternal strain H-2 K antigens.