Serological H-Y antigen in the female chicken occurs during gonadal differentiation.

In the chicken, serological H-Y antigen is specific for the female sex. Male gonad differentiation can be experimentally influenced by estrogens, resulting in the transient formation of an ovotestis. The sex-inverted gonad becomes positive for H-Y antigen. Therefore, the question arises whether, in normal gonadogenesis also, the female gonad at the indifferent stage, before estrogens are produced, is negative for H-Y antigen. Here we show that this is indeed the case. The female gonad becomes positive for H-Y antigen when the ovary starts its organotypic differentiation at about day 6 1/2 of embryonal development. It is assumed that estrogens are responsible for the occurrence of H-Y antigen. This finding supports the view that H-Y antigen plays a role in primary ovogenesis in the chicken.