Preliminary study of histamine H 4 receptor expressed on human CD4 + T cells and its immunomodulatory potency in the IL-17 pathway of psoriasis.

BACKGROUND: Previous studies have shown the expression of histamine H4 receptor (H4R) on CD4+ T cells, especially human CD4+ Th 2-polarized T cells.

OBJECTIVE: This study aimed to investigate the role of H4R on these effector T cells in psoriasis.

METHODS: We enrolled three patients each with active psoriasis, inactive psoriasis, scalp seborrheic dermatitis, and three normal controls, and compared the basal expression of H4R mRNA in their peripheral blood CD4+ T cells. Then, we identified H4R expression in dermal CD4+ T cells. Furthermore, we investigated H4R expression after stimulating separated peripheral blood CD4+ T cells with several inflammatory cytokines.

RESULTS: The results showed higher H4R expression in the active psoriasis group compared to the inactive psoriasis group. It was interesting that interleukin (IL)-23, which is a representative cytokine contributing to Th 17 cell differentiation, stimulated H4R expression significantly. After adding a selective H4R antagonist (JNJ-7777120) while the CD4+ T cells were polarized into Th 17 cells, we observed a tendency toward suppressed IL-17 secretion.

CONCLUSIONS: Histamine stimulation influences the IL-17 pathway in psoriasis via the fourth histamine receptor subtype, H4R, on CD4+ T cells. The immunomodulatory roles of H4R suggest its potency as a new therapeutic target for obstinate psoriasis.