MHC antigens on mouse trophoblast cells: paucity of Ia antigens despite the presence of H-2K and D.

The presence of Ia antigens was examined on the surface of trophoblast cells isolated from mouse placentae resulting from mating C57BL/6 female and CBA male mice. A sensitive immunolabeling method was employed in which cells were treated with polyspecific anti-Ia (A.TH anti-A.TL) or monoclonal anti-Ia.17 antibody followed by 125I-labeled protein A and examined with the aid of quantitative radioautography. No appreciable levels of Ia antigens were detectable between days 12 and 17 of pregnancy, although significant amounts of H-2D were always found on the trophoblast cells from the same placentae, and spleen cells as well as thymocytes from control animals always showed the expected degree of labeling for Ia antigens.