It has been reported that histamine induces CD86 expression and chemokine production in human immature monocyte-derived dendritic cells (MoDCs), which can be blocked by both H₁- and H₂-receptor antagonists.

We sought to examine whether the efficacy of H₁-type antihistamines can be assessed by using MoDCs.

We examined the suppressive effects of 1 H₂-type antihistamine (cimetidine) and 5 different H₁-type antihistamines (cetirizine, diphenhydramine, ketotifen, olopatadine, and emedastine) on the induction of CD86 and IL-8 production by MoDCs from 23 healthy individuals stimulated with histamine. We also examined the responses of MoDCs from 13 patients with chronic urticaria to these antihistamines, and compared the in vitro efficacy with the actual clinical response to antihistamines evaluated by patient and physician assessments.

All the antihistamines we examined suppressed the increase of CD86⁺ cells after histamine stimulation in a dose-dependent fashion, and all H₁-type antihistamines were more efficacious than cimetidine. IL-8 production stimulated with histamine was also suppressed by cetirizine, ketotifen, and olopatadine. Unexpectedly, the suppressive effect of these antihistamines on the CD86 augmentation was highly variable among different healthy control participants. Interestingly, in 10 of 13 cases of chronic urticaria, this in vitro analysis of antihistamines correlated with the clinical response to antihistamines.

This study suggests that the evaluation of antihistamines using MoDCs can be a useful method for the screening of effective antihistamines, for the comparison of the efficacy of antihistamines, and for predicting the efficacy of antihistamines on an individual basis.