Similar disaggregation-re~ggregation experiments show that human fetal lung can be enzymatically dispersed into a single cell population and that it reconstitutes histotypically in the image of the organ of derivation, complete with the epithelial cell-surface A/B antigens. Preliminary experiments also point to the ability of anti-A/B sera to abrogate (experimental) organogenesis. Various species of anti A/B reagents (e.g. monoclonal IgG) are to be tried, with the situation of the human embryo in utero as a point of reference. HLA ANTIGENS ON HUMAN TROPHOBLAST CELLS. Barbara Montgomery and Peeyush K. Lala, Dept. of Anatomy, McGill University, Montreal, Canada H3A 2B2. Occurrence of major histocOmpatibility (HLA) antigens on the surface of human trophoblast cells was examined with a sensitive radioautographic technique. Placentae recovered from therapeutic abortion at 7-8 weeks gestation were dispersed in Ca ++ , Mg +÷ free buffered medium containing 0.3% collagenase. After washing, red cell lysis and clump removal cell suspensions were treated at 4°C with 1/20 dil of a monoclonal mouse anti-HLA antibody (directed against framework components of HLA-A, B or C) followed by 125I-labeled Protein A (l~g/ml, 40 Ci/g). Tissue controls were provided by Ficoll-Paque separated adult human peripheral blood lymphocytes (PBL), and serum controls by normal mouse serum (NMS). Relative labeling intensity was assessed from silver grain count distribution on cells per unit area in radioautographs. There was no direct labeling of trophoblast cells or PBL with 125I-Protein A. Following treatment with anti-HLA ab, strong labeling was seen in most or all PBL, as well as leukocytes, erythroblasts and decidual cells in placentae. Trophoblast cells showed weaker but nevertheless positive specific labeling, the intensity of which varied amongst different placentae. These results indicate the presence of HLA (A, B or C) antigens on 7-8 week old trophoblast cells, the density of which is lower than on adult and fetal leukocytes or erythroblasts. (Supported by the MRC Canada).
0NTOGENY & KINETICS OF THE PLACKNTAL IMMUNOABSORBENT
& 1"noma8 G. W e q m a n n . Dept. of Immunology, Univ. of Alberta Edmonton, Canada T6G 2H7 In previous reports w e h a v e presented evidence for the expression of paternal H-2K antigens on the allogeneic murlne