H4R is highly expressed on keratinocytes from patients with atopic dermatitis, and its stimulation induces keratinocyte proliferation. This might represent a mechanism that contributes to the epidermal hyperplasia observed in patients with atopic dermatitis.

fect was mediated via H 2 R and H 4 R in monocytes and mDC. Conclusion: Monocytes and mDC have similar histamine receptor repertoires with regard to H 1 R, H 2 R and H 3 R, but H 4 R expression is higher on mDC. Histamine stimulation shows similar functional effects on both cell types, i.e., downregulation of TLR3-induced IP-10 production. This might be a new mechanism how histamine fosters a Th2 milieu.

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