Neuroendocrine-Immune Interactions

Abstract

The role of the neuroendocrine system in influencing both immune development and function has become an area of active research within many model systems, including the chicken. It is now clear that the neuroendocrine system can exert immediate feedback regulation on the immune system as well as control specific aspects of immune differentiation and development. The primary lymphoid organs of avian species (i.e., the thymus and the bursa of Fabricius) are also known to function as endocrine organs. These produce hormonal products that influence the development of lymphoid cells and that may feed back on the neuroendocrine system. In conjunction with the endocrine activities of the primary lymphoid organs, immune and accessory cells are known to produce a variety of secreted products or cytokines that have the potential not only for the regulation of immune function but also for mediating neuroendocrine activities. Finally, it has been demonstrated in a variety of species that leukocytes are capable of producing endocrine mediators previously believed to be produced only under the direct control of the hypothalamic-pituitary axis. Thus, there are numerous possibilities for bidirectional interactions between the immune and neuroendocrine systems. This discussion focuses primarily on these interactions with an emphasis on the means by which the hormonal mediators, growth hormone and thyroid hormone, may affect the thymus and the thymic microenvironment. The role of the adrenocorticoids and gonadal steroids in regulating immune function and their involvement in immune feedback circuits are also discussed.

Salmonella enterica Serovar Pullorum Persists in Splenic Macrophages and in the Reproductive Tract during Persistent, Disease-Free Carriage in Chickens

“…At high concentrations, gonadal steroids appear to have an immunosuppressive effect. At lower concentrations, the hormones appear to have a regulatory role, acting both to increase and to suppress immune activity in a variety of ways (19), though little is known of their effects on bacterial infections. However, the numbers of both lymphocytes and macrophages in the reproductive tract at sexual maturity (39) and the previously reported increases in numbers of these cells and in antibody production in the reproductive tract in experimental Salmonella serovar Enteritidis infection (40) suggest that chickens have a strong immune response in the reproductive tract.…”

Androgen control of immunocompetence in the male house finch,Carpodacus mexicanusMüller

“…Corticosterone in birds is generally immunosuppressive (Marsh and Scanes, 1994). This steroid is immunosuppressive also in some (rodents: Collins and Deas, 1986;Stewart et al, 1988;review: Sapolsky, 1992) although not other vertebrates, in which it rather enhances immunocompentence (side-blotched lizard, Uta stansburiana: Svensson et al, 2002).…”

Localization of Neuropeptides in Endocrine Cells of the Chicken Thymus.

“…Intrathymic interactions have been implicated in the control of the thymic microenvironment involving T-cell differentiation and maturation. In the avian thymus, intrathymic interactions via thymic hormones, avian thymic hormone and thymulin, are generally accepted, as they are in mammals [10]. The avian thymus contains endocrine cells as one of its major cellular components.…”