Ontogeny of MHC class II antigens in pigs.

Cells constitutively expressing MHC class II antigens have been studied in the course of prenatal development in the Minnesota miniature pig. Frozen sections, cell suspensions and peripheral blood mononuclear cells were examined by using the HL-40 monoclonal antibody cross-reactive with a light chain determinant of the SLA-D molecule (MHC class II porcine antigen). It could be demonstrated that the yolk sac contained cells expressing SLA-D antigens as early as the 24th day, the liver and the spleen on the 39th day of gestation. Splenic cells bearing SLA-D molecules formed periarteriolar structures. Except the spleen, peripheral blood, lymph nodes, bone marrow and intestinal wall were the main sites of SLA-D expression in the perinatal period of the pig.