In normal mammals, an excellent correlation has been demonstrated between H-Y antigen positivity and normal testicular development. Furthermore, in normal mammals, no ovarian tissue has been found with H-Y antigen positivity. These observations have led some investigators to consider that the H-Y antigen plays the pivotal role in sex determination. In fact, it has been stated that in a very strict sense, the primary (gonadal) sex of mammals is determined not so much by the presence or absence of the Y chromosome, but by the expression or non-expression of the H-Y antigen. However, in patients with various problems of sexual differentiation, the expression or non-expression of the H-Y antigen does not correlate well with the presence or absence of testicular development. There are many exceptions as illustrated by the case material reported. For example, an XX/XY chimeric individual was H-Y antigen-positive but had both testicular and ovarian tissue. Furthermore, there were 46,XX true hermaphrodites who were both H-Y antigen positive and H-Y antigen negative and several 46,XY H-Y antigen positive patients had either only a unilateral testis or no testes at all. Some of these patients had streak gonads. Thus, on the basis of human pathological material, it is very difficult to correlate the presence of H-Y antigen with testicular formation. At the same time, it is impossible to exclude the possibility that H-Y antigen is essential for testicular formation. If it is assumed that H-Y antigen is essential, data from XX/XY chimerism and data from asymmetrical gonadal differentiation suggest that in order for H-Y antigen to result in testicular formation, at least one additional locus on the Y chromosome is essential. The presence in streak gonads of hilar cells, rete tubules, and wolffian remnants in patients who were H-Y antigen-positive makes it very difficult at this time to define precisely the gonadal phenotype with which H-Y antigen positivity should be correlated. In view of the inconsistencies just cited, the clinical application of H-Y antigen postivity or negativity must be limited by these considerations.
