Histamine receptor antagonist partially blocked IL-17 amplification by basophils. (A) T_EM were cultured in the presence of IL-2 plus IL-3 with or without basophils in the presence or absence of antagonists to H₁R, H₂R or H₄R (10⁻⁵M). After 4 days, IL-17, IL-22, and IFN-γ secretion was measured using ELISA. (B) T_EM were cultured in the presence of IL-2 plus IL-3 with or without 5μM histamine or cocultured with basophils. After 5 days, cytokine production was measured using ELISA. Data represent means ± SEM for 4 donors. *P < .05; **P < .01; ***P < .001.