Objective: In earlier experiments the immune cells of HDC gene knock-out (HDC-KO) mice contained significantly more serotonin, than those of the wild ones. It was supposed that serotonin, being another biogenic amine, replenishes histamine deficiency. Now we extended our earlier studies to the investigation of the levels of other hormones (adrenocorticotropic hormone [ACTH], beta-endorphin, triiodothyronine [T(3)]) in this knockout model.
Methods: Peritoneal lavage fluid samples and thymuses were gained from HDC-KO and wild type mice. Their cells were prepared for flow cytometry and confocal microscopy by using specific antibodies to the three hormones (1st antibodies) and 2nd antibody to the 1st antibodies. The results of wild type and KO animals were compared.
Results: In KO animals the ACTH content in mast cells was significantly reduced and in thymic lymphocytes halved. Endorphin content was reduced both in peritoneal and thymic lymphocytes as well as in mast cells. T(3) content showed a two and a half-fold elevation in the monocyte-macrophage-granulocyte group. The confocal microscopic analysis showed the characteristic picture of HDC-KO mast cells, their cytoplasm being almost free of granules.
Conclusion: Knock-out of the histidine decarboxylase gene causes a general endocrine imbalance in the hormones which are related to histamine, inside the immune cells. Levels of some hormones are elevated, others decreased.