Stress differentially affects the systemic and leukocyte estrogen network in common carp.

Both systemic and locally released steroid hormones, such as cortisol and estrogens, show immunomodulatory actions. This research gives evidence that circulating and leukocyte-derived estrogens can be involved in the regulation of the immune response in common carp, during homeostasis and upon restraining stress. It was found that stress reduced level of blood 17β-estradiol (E2) and down-regulated the gene expression of components of the "classical" estrogen system: the nuclear estrogen receptors and the aromatase CYP19, in the hypothalamus, the pituitary and in the ovaries.

A role for multiple estrogen receptors in immune regulation of common carp.

Estrogens are important for bi-directional neuroendocrine-immune interaction. They act via nuclear estrogen receptors (ERα and ERβ) and/or G-protein coupled receptor - GPR30. We found expression of ERα, ERβ and GPR30 in carp lymphoid tissues and head kidney monocytes/macrophages, neutrophils and lymphocytes.

A role for melatonin in maintaining the pro- and anti-inflammatory balance by influencing leukocyte migration and apoptosis in carp.

Melatonin is responsible for the synchronization of many physiological processes, including the immune response. Here we focus on the expression of melatonin MT1 receptors in/on leukocytes, and on the effects of melatonin administration on the inflammatory processes of carp. For the first time, we showed that fish leukocytes express MT1 receptors, implicating direct responsiveness to melatonin stimulation.

Activity of the hypothalamus-pituitary-interrenal axis (HPI axis) and immune response in carp lines with different susceptibility to disease.

The stress response transmitted by the HPA axis is one of the best examples of neuroendocrine-immune interactions that are critical for survival. Analogous to the situation in mammals, the stress response in fish is characterized by the activation of the hypothalamo-pituitary-interrenal axis (HPI). Effects of cortisol on the fish immune system comply with findings in mammals and suggest that the differences in sensitivity to stress will influence the immune response and as a consequence of survival.