[A new observation of an H-Y antigen positive 46, XX male (author's transl)].

A new serologic test for detecting the H-Y antigen by indirect fluorescence performed on purified lymphocytes was developed. It allowed us to demonstrate H-Y antigen in an 46, XX male. The presence of this antigen explains why the primitive gonad underwent testicular differentiation. Several mechanisms could account for the presence of H-Y antigen. Mosaicism or translocation of an X on a Y or an autosome may prevent detection of a Y chromosome. Alternatively, a Y chromosome may have disappeared during embryogenesis, The last hypothesis suggests that an autosome may carry a structural gene coding for H-Y antigen; in this case thye Y chromosome would act only as an accessory regulating gene.