The identification of human H-Y antigen and testicular transformation induced by its interaction with the receptor site of bovine fetal ovarian cells.
beta 2m(-), HLA (-) Daudi human male Burkitt lymphoma cells excreted a group of protein subunits that shared three distinctive characteristics; their conspicuously longer half-lives compared to more hydrophilic Daudi excreted proteins, their tendency to form progressively larger polymers by means of interchain disulfide bridges, and the extreme hydrophobicity of these polymers. The plasma membrane of extragonadal somatic cells absorbed 1.2 to 2.8% of these hydrophobic proteins. The unoccupied H-Y receptor sites residing on the plasma membrane of bovine fetal ovarian cells, on the other hand, selectively absorbed polymers of 18,000 mol. wt. subunits, and this antigen-receptor interaction, if allowed to continue for five days, induced the formation of tunica albuginea and seminiferous tubules in bovine XX embryonic indifferent gonads. In this manner, human H-Y antigen excreted by Daudi cells has functionally been identified as a series of polymers derived from 18,000 mol. wt. subunits. While, the H-Y antigenic determinants were retained even by the largest polymeric form that became irreversibly water insoluble, the receptor binding activity was shown only by 36.8% of the available polymeric forms of 18,000 mol. wt. subunits, at the most. Nevertheless, once bound to the receptor site, these polymers were rapidly reduced to the monomeric form on the plasma membrane of bovine fetal ovarian cells. Accordingly, the 18,000 mol. wt. monomer might actually represent the functional form of H-Y antigen.