In vitro effects of steroid hormones on IgM-secreting cells and IgM secretion in common carp (Cyprinus carpio)

The effects of steroid hormones on in vitro IgM-secreting cells (IgMSC) and IgM secretion by lymphocytes of the lymphoid organs in common carp, Cyprinus carpio were examined by ELISPOT and ELISA assay, respectively. Cells isolated from peripheral blood (PB), spleen and head kidney were cultured for 12, 24 and 48 h either in the absence or in the presence of steroid hormones, i.e. cortisol, testosterone, 11-ketotestosterone (11-KT), and estradiol-17beta (E(2)) at doses of 1, 10 and 100 ng/ml. Cortisol reduced the IgMSC numbers and IgM secretion by cells from all organs. In addition, cortisol induced apoptosis in lymphocytes from all organs. High dose of testosterone showed tissue-specific functions; it reduced the number of IgMSC and amount of IgM secretion by cells from spleen and head kidney, but not in PB, though IgM secretion was suppressed. However, no effects of sex steroids were observed in this study. The results show that sex-specific steroid hormones may have no immunosuppressive effects in common carp.