[Hormones and immunity to parasitic apicomplexans]

Several studies revealed a close functional relations between the immune, nervous and endocrine systems which communicate between each other using the common mediators and their receptors. The immune cells not only receive signals from the endocrine system but also produce numerous hormones, usually after stimulation with antigens including parasites antigens. On the other hand, parasites are able to exploit hormonal microenvironment within the host to establish an infection and avoid the eradication by evolving receptors for host hormones. Some parasites produce also steroid hormones and alter host hormones levels. Increasing numbers of prophylaxis and therapy procedures involve hormones as main or supplementary components (e.g., estrogens, dexamethasone or insulin). The aim of this paper is to present new literature data concerning the immunomodulatory effect of selected hormones in infections caused by two parasitic apicomplexans: Toxoplasma gondii and Plasmodium spp. In addition to sex- and pregnancy- associated hormones which determine dimorphic immune responses in females versus males, the action of other hormones of great physiological importance will also be discussed.