A note for myself
Histamine is produced by CD4T, CD8T and basophils by transferring histidine with a catalysis of histidine decarboxylase (HDC). In immune system, histamine can cause anaphylactic response and regulate cytokine production by T and APC,  influence T cell proliferation and affect T cell polarization. There are 4 receptor proven to be histamine receptors, H1R, H2R , H3R and H4R. With antagonist treatment against H1R or H2R, or gene deficient mice test, it showed that a blockage of signalling from H1R or H2R can inhibit early phase of EAE and relieve EAE.  On the contrary, HDC deficient mice appeared increased levels in IFN-r, TNF, MCO-1, leptin, IgE and more severe EAE and CNS inflammation. Moreover, IL-3, IL-17, and IL-6 increased in mRNA in HDC KO mice. HDC Ko mice also born abnormal mast cells which are critical for the full manifestation of the disease.