Effects of atopy and grass pollen season on histamine H4 receptor expression in human leukocytes

H4R mRNA is predominantly expressed in peripheral blood leukocytes, and total H4R expression levels are unrelated to atopy or grass pollen season. Atopy-independent seasonal variation in truncated H4R expression might affect putative negative regulation of full length H4R during high grass pollen season. If verified, this should be considered during the design of drugs targeting H4R to treat allergic inflammation, particularly for seasonal allergic rhinitis.