A substance secreted by rat Sertoli cells induces feminization of embryonic chick testes in vitro.

Male and female gonads from 7- to 9-day-old chick embryos were cultured for 6 days in Sertoli cell-conditioned medium or in serum-free medium to investigate the possible effect of substances secreted by rat Sertoli cells on chick gonad development. Histological analysis showed that whereas all female gonads proceed through normal ovarian development in both culture media, most of male gonads showed clear feminization only when cultured in Sertoli cell-conditioned medium; male gonads cultured in serum-free medium developed as normal testes. Because the only substance detected in our conditioned medium with the potential to cause these effects was sex-specific antigen (Sxs), our results provide further evidence that Sxs antigen may play a role in sexual differentiation in birds, and probably in mammals.

Daudi supernatant, unlike other H-Y antigen sources, exerts a sex-reversing effect on embryonic chick gonad differentiation.

In vitro cultures of intact chick gonads (organ cultures) and reaggregation cultures of dispersed gonad cells (roller cultures) were made. Gonads or gonad cells from 7-day-old chick embryos, at the stage when sex-specific differentiation begins, were cultured in the presence of presumed H-Y antigen-containing supernatants, or co-cultured in the presence of H-Y antigen-producing cell lines. The H-Y antigen-producing cells tested were of human, mouse, bovine and chicken origin. During organ culture, addition of supernatant of the human lymphoma cell line Daudi, or co-culture with Daudi cells, stimulated a clear proliferation of the germinal epithelium in male gonads, indicating feminization. A similar effect was obtained by treatment with estradiol. In reaggregation culture, the increase in nuclear size of germ cells was chosen as a parameter for feminization. A significant increase of germ cell nuclear size was observed in gonads cultured in the presence of Daudi supernatant. In both organ cultures and reaggregation cultures, other tested H-Y antigen sources and semi-purified H-Y antigen fractions did not exert significant effects on differentiation of the gonads or on the average area of the germ cell nuclei. These findings suggest that it is not H-Y antigen, but another protein produced by Daudi cells, that might be responsible for the sex-reversing effects.

Genetic control of the cellular in vitro response to the H-Y antigen in the rat.

The immune response against the male-specific H-Y antigen has been studied in RT1 congenic rat strains by assaying the cytotoxic and proliferative response in vitro after in vivo priming. The capacity to respond is associated with the RT1a and RT1n major histocompatibility haplotypes, and nonresponsiveness with the RT1u haplotype. Both, genes of the RT1.A region, which encodes class I antigens, and of the RT1.B/D region, which includes class II and transporter genes, are involved in the genetic control. In F1 hybrids haplotype preference of H-Y restriction occurs in favor of RT1a. Cross-priming can be induced in F1 hybrids by parental cells for RT1a-restricted cytotoxic and proliferative T cells. Allopriming is successful only in the RT1a-carrying strain, whereas xenopriming with mouse cells could not be elicited. The results are discussed in the context of current views on processing and presentation of antigens, and their relevance for transplantation is pointed out.