Cytolytic and fluorescent detection of H-Y antigen on preimplantation mouse embryos.

Monoclonal antibodies to histocompatibility (H-Y) antigen, of IgM subclass, were used to immunologically determine the sex of mouse embryos prior to transfer to pseudopregnant recipients. Two experiments were performed, one using cytolysis of H-Y positive embryos and the other using binding of a Fluorescein Isothiocyanate-(FITC) labeled second antibody. Eight- to 16-cell embryos used in the cytolytic assay were cultured in Whitten's Medium without bovine serum albumin (WM), to which monoclonal antibody and normal guinea pig serum were added. Embryos were classified as affected or unaffected, based on morphology of the embryo and its blastomeres. A total of 550 embryos were cultured; 294 (53.5%) were scored as unaffected and 263 of these were transferred to recipients. Forty-three (81.1%) of 53 pups born were female. Morulae and early blastocysts were used in the FITC-labeled second antibody assay. Embryos were cultured in WM containing monoclonal antibody, washed and placed in drops of WM containing FITC-labeled anti-IgM. Following another wash embryos were individually evaluated at 200X for fluorescence. Fifty-five percent (169 of 305) of the embryos displayed cell-specific fluorescence. A total of twenty-three pups, 18 males (78.3%) and five females (21.7%), were born following transfer of 156 fluorescing embryos. Four male (17.4%) and nineteen female (82.6%) pups resulted from embryos classified as non-fluorescing.