アレルギー性鼻炎診療の最近の進歩

抄録

Allergic rhinitis (AR) is a type I allergic disease of the nasal mucosa characterized by sneezing, watery rhinorrhea, and nasal congestion. A recent epidemiological survey revealed that nearly half of the population develops AR. Until recently, Th2 cells, which produce IL-4, IL-5, and IL-13 in an antigen-dependent manner and induce type 2 immune responses, were thought to play a major role in the pathogenesis. However, since the recent discovery of group 2 innate lymphoid cells (ILC2s), which also produce type 2 cytokines in response to IL-25, IL-33, TSLP released from epithelial cells, involvement of ILC2s also in the development of AR has been proven. Histamine is a major chemical mediator that induces AR symptoms through binding to the histamine H₁ receptor (H1R). We found that histamine-mediated stimulation of H1R induced upregulation of the H1R gene expression and that the elevated receptor expression levels in the nasal mucosa increased histamine signaling to exacerbate the symptoms of AR. Antihistamines block histamine signaling triggered via the H1R, suppress histamine-induced upregulation of transcriptional activation, and suppress basal transcription of H1R in the absence of histamine, which may reflect the inverse agonist action of antihistamines. Allergen immunotherapy can provide long-term benefits in patients with AR by modulating the immune responses. Sublingual immunotherapy (SLIT) with a standardized Japanese cedar (JC) pollen significantly improved the nasal symptoms and AR-related sleep disturbance in patients with JC pollinosis. Dual SLIT with JC pollen and house dust mite (HDM) suppressed both JC pollen-induced seasonal and HDM-induced perennial nasal symptoms in bisensitized patients with AR. Dual SLIT was more effective in suppressing nasal obstruction at the peak of JC pollen dispersal period than mono SLIT with JC pollen. In this paper, we describe the recent advances in the management of allergic rhinitis, along with our own research findings.