Histidine Decarboxylase Expression in Human Monocytes, Macrophages and Macrophage Subsets

From Molecular Science to the Treatment of Allergy Sorry, there is no abstract. Read the first few lines of the text instead! Human blood monocytes contain substantial amounts of histamine which may be released on appropriate stimulation, e.g. by C5a [1]. Monocytes also exhibit histidine decarboxylase (HDC) activity and express HDC mRNA, indicating that the histamine is generated by the cells themselves [2]. Here we studied the expression of HDC mRNA in monocytes and macrophages and its regulation by histamine liberating agents such as C5a and calcium ionophore. Furthermore, substances known to affect monocyte functions were included, e.g. phorbol ester and lipopolysaccharide (LPS) which activate macrophages, and glucocorticoids which inhibit most of the inflammatory activities of macrophages.