Expression of the PACAP-immunoreactivity in the Lymphoid Organs of the Duck

Abstract Introduction: The interactions occurring between nervous and immune systems are well documented. These interactions involve several types of chemical messengers including hormones, cytokines, classic neurotransmitters and neuropeptides. It has been observed that the lymphoid organs receive a dense peptidergic innervation and immune cells produce neuropeptides. Neuropeptides, in turn, are involved in the regulation of the inflammatory processes and in the maturation of the lymphoid organs. Several studies have demonstrated that the immunomodulatory neuropeptides and their receptors are expressed in the thymus and bursa of fabricius. PACAP is a glucagon/VIP/secretin family peptide. It was originally isolated from the ovine hypothalamus and then it was found in the autonomic nervous system. PACAP is involved in the regulation of the hypothalamic-pituitary function, neurotransmission and neuromodulation. In the immune system, PACAP is expressed in lymphoid tissues of the rat and in the lymphocytes of the duck GALT. PACAP, therefore, could be a messenger of the dialogue between nervous and immune system. It may have a role in the regulation of the inflammatory processes by stimulating histamine and serotonin and modulating the production of the cytokines in immune cells. Methods: Immunohistochemistry on paraffin-embedded sections of thymus and bursa of fabricius of the duck of different ages by using an antibody anti-PACAP38. Results and Discussion: In the thymus, PACAP-immunoreactivity was found in lymphoid cells and, with a lesser extent, in epithelial reticular cells. The immunoreactive lymphocytes were primarily observed in the interlobular septa in close vicinity to the interlobular veins. The number of positive lymphocytes increased with ageing. In the bursa of fabricius, PACAP-IR was found in nerve fibres and in a few lymphoid cells. These results suggest that PACAP could play a role in the maturation and involution of these organs and in the immune functions.

ABSTRACT: The interactions occurring between nervous and immune systems are well documented. These interactions involve several types of chemical messengers including hormones, cytokines, classic neurotransmitters and neuropeptides. It has been observed that the lymphoid organs receive a dense peptidergic innervation and immune cells produce neuropeptides. Neuropeptides, in turn, are involved in the regulation of the inflammatory processes and in the maturation of the lymphoid organs. Several studies have demonstrated that the immunomodulatory neuropeptides and their receptors are expressed in the thymus and bursa of fabricius. PACAP is a glucagon/VIP/secretin family peptide. It was originally isolated from the ovine hypothalamus and then it was found in the autonomic nervous system. PACAP is involved in the regulation of the hypothalamic-pituitary function, neurotransmission and neuromodulation. In the immune system, PACAP is expressed in lymphoid tissues of the rat and in the lymphocytes of the duck GALT. PACAP, therefore, could be a messenger of the dialogue between nervous and immune system. It may have a role in the regulation of the inflammatory processes by stimulating histamine and serotonin and modulating the production of the cytokines in immune cells. Methods: Immunohistochemistry on paraffin-embedded sections of thymus and bursa of fabricius of the duck of different ages by using an antibody anti-PACAP38. Results and Discussion: In the thymus, PACAP-immunoreactivity was found in lymphoid cells and, with a lesser extent, in epithelial reticular cells. The immunoreactive lymphocytes were primarily observed in the interlobular septa in close vicinity to the interlobular veins. The number of positive lymphocytes increased with ageing. In the bursa of fabricius, PACAP-IR was found in nerve fibres and in a few lymphoid cells. These results suggest that PACAP could play a role in the maturation and involution of these organs and in the immune functions.