Phylogeny of the neuroendocrine-immune system: Fish and shellfish as model systems for social interaction stress research in humans

Significant interactions among various physiological systems and between an organism's physiological and psychological structures are evident throughout phylogeny. Environmental stimuli induce neuroendocrine responses that include the activation of the sympathetic nervous system and of the hypothalamic-pituitary-adrenal (HPA) axis, and that modulate cellular and humoral host defense mechanisms from the invertebrates to humans. Because increased levels of HPA products are among the most consistent physiological responses to stress, and bacause cell-mediated immune (CMI) mechanisms are crucial to the initiation, propagation, and regulation of antigen-specific immune responses, this review focuses on the phylogeny of HPA-CMI interaction under basal conditions and following stressful stimuli.

Research has characterized several paradigms for the study of the physiological outcomes to a variety of stressors. In recent decades, a substantial literature has emerged that describes the neuro-endocrine-immune response to social confrontation in invertebrates and in vertebrates. The social confrontation paradigm provides an ideal model for the elucidation of the phylogeny of the HPA-CMI interactive system to a specific stressful stimulus. We have characterized the neuroendocrine-immune outcomes of social confrontation in fish. Our data help to explain physiological and pathological mechanisms in fish. Implications of this body of knowledge to clinical medicine and aging are discussed.