Abstract
In this issue of Cancer Cell, Li et al. show that histamine released in allergic reactions and from tumor cells attenuates immunotherapy response. Histamine H(1)-receptor (H(1)R) signaling induces an M2-like phenotype in tumor-associated macrophages and increases VISTA expression, suppressing CD8(+) T cell function. Antihistamines reverse these effects and improve the efficacy of immunotherapy.