Evidence for the presence of immunoreactive POMC-derived peptides and cytokines in the thymus of the goldfish (Carassius c. auratus).

The presence of immunoreactive pro-opiomelanocortin (POMC)-derived peptides (adrenocorticotropin hormone, beta-endorphin, alpha-melanocyte-stimulating hormone) and of cytokine-like molecules [interleukin (I)-1 alpha, IL-1 beta, IL-2, Il-6, tumour necrosis factor-alpha] was demonstrated in periodic acid-Schiff-positive epithelial cells in the thymus of the goldfish (Carassius c. auratus) using immunocytochemical procedures. POMC-derived peptide- and cytokine-like molecules were localized in the same cell type. Lymphocytes were negative for all the above mentioned molecules. Despite the smaller number of cells positive for neuropeptide- and cytokine-like molecules, our findings suggest that immune-neuroendocrine interactions are likely to occur in the thymus of goldfish.