Immunohistochemical localization of neuroendocrine cell types in the immune system of the chicken

Abstract

The objective of the current study was to provide solid evidence for the existence of neuroendocrine cells within the immune system of the chicken. This was achieved with an immunocytochemical approach using monoclonal antibodies against turkey chromogranin A (CgA). Chromogranin A is indeed the most classic marker protein for neuroendocrine tissue that is most frequently cited in the context of neuroendocrine neoplasm diagnosis. To our knowledge, the present study was the first one to be successful in this respect. CgA-immunoreactive (ir) cells were observed in both central immune organs, the thymus and the bursa, although expression was generally spoken much higher in the thymus than in the bursa. In both organs, expression increased with age; the most intensive staining patterns were observed in 13-week old animals in both organs. Interestingly, in the thymus, a neuron-like cell type was discovered; this observation confirmed an earlier observation of a NO-synthase-positive neuron-like cell type in the thymus. CgA expression was dramatically increased by viral infection with IBDV in both bursa and spleen 8 days post-inoculation with the virus. It can be speculated that this CgA upregulation is correlated with an upregulation of immunostimulatory substances meant to aid in regeneration of the damaged immune tissue, though this hypothesis would of course need to be proven.