The mRNA expression and secretion of granzyme B are up-regulated via the histamine H2 receptor in human CD4⁺ T cells

Granzyme B (GZMB), a serine protease with cytotoxic and immunomodulatory functions, shows elevated levels in blood plasma of patients with atopic dermatitis (AD). It has been observed that GZMB expression in CD4⁺ and CD8⁺ T cells is higher in lesional skin in AD than in healthy skin. Since histamine is present in high concentration in the skin of AD patients, we investigated the regulation of GZMB in human CD4⁺ T cells by histamine.

Naïve CD4⁺ T cells polarized into Th2 cells, total CD4⁺ T cells treated with IL-4 for 72 h and CD4⁺ T cells isolated from healthy donors and AD patients were investigated. The cells were stimulated with histamine or with different histamine-receptor agonists. Gene expression was evaluated by RNA-Seq. GZMB mRNA expression was detected by quantitative real time PCR, whereas GZMB secretion was measured by ELISpot and ELISA. T cell degranulation was evaluated by flow cytometry using CD107a surface expression as a degranulation marker.

By RNA-Seq, we identified the up-regulation of various genes of the cytotoxic pathway, in particular of GZMB, by histamine in Th2-polarized CD4⁺ T cells. In Th2-polarized CD4⁺ T cells and in CD4⁺ T cells activated by IL-4 the mRNA expression of GZMB was significantly up-regulated by histamine and by histamine H2 receptor (H2R) agonists. The induction of GZMB secretion by histamine was significantly higher in CD4⁺ T cells from AD patients than in those from healthy donors. CD107a surface expression was up-regulated by trend in response to histamine in Th2-polarized CD4⁺ T cells.

Our findings may help to elucidate novel mechanisms of the H2R and to achieve a better understanding of the role of GZMB in the pathogenesis of AD.