Research PapersSex- and stress-steroids interactions and the immune system: evidence for a neuroendocrine-immunological sexual dimorphism
Section snippets
Sexual dimorphism in the immune response
In the bidirectional communication between the endocrine and the immune systems, a sexual dimorphism seems to exist at both levels. Sex steroids play an important modulatory role in the regulation of the immune function explaining the sexual dimorphism observed in the immune response. Indeed compared with male mice or rats, females have higher levels of serum immunoglobulins, greater and more prolonged antibody responses, shorter skin allograft rejection time, as well as a higher incidence of
Sexual dimorphism in the endocrine response
Besides the sexual dimorphism in the immune response, there is also a sexual dimorphism in the pituitary-adrenal function. Compared to males, female rats have higher basal levels of plasma corticosterone, higher diurnal rise in plasma corticosterone, higher corticosteroidogenesis by adrenal slices in vitro, and ACTH or stress produce higher and more prolonged elevated plasma corticosterone levels in female than in male rats. There is also a sex difference in rat pituitary glucocorticoid
Modulatory effects of the sex-steroids on the hypothalamo-pituitary-adrenal and immune axis responses to LPS
In the bidirectional communication between the endocrine and immune system, it has been suggested that inflammation-induced activation of the hypothalamo-pituitary-adrenal (HPA) axis may represent a potent negative feedback mechanism through which the immune system, by stimulating the HPA axis and therefore the production of immunosuppressive glucocorticoids, avoids an overshoot of the inflammatory and febrile effect (9) during the acute phase response (Figure 1 ). This production of
Influence of sex steroids on LPS-induced immune response
We also investigated whether gonadal steroids do influence or modulate the LPS-induced immune response. To this purpose, we measured the effect of LPS on the release of plasma TNFα in intact mice of both sexes, in gonadectomized mice as well as in gonadectomized mice receiving sex hormone replacement therapy.
Plasma TNFα levels in basal conditions did not vary with the sex of the mice or with bilateral gonadectomy alone or followed by sex steroid treatment. Plasma TNFα levels were similar in all
Sexual dimorphism of the HPA axis function during development
Because testosterone levels vary over development, and to determine whether physiological testosterone changes may modulate the HPA axis response to endotoxins, we measured plasma corticosterone response to endotoxin in prepubertal (7, 15, and 30-d-old) mice—these are periods of development with low testosterone levels—and in postpubertal and adult mice (45 and 60-d-old)—periods of development with normal testosterone levels (16).
The results obtained at 7 and 15 d of age show the existence of
Acknowledgements
This research was supported by the Swiss National Fondation, Grants No. 31-39749.93 and 31-050748.97/1. The authors wish to thank Mrs. L. Trieste for typing the manuscript.
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