Lack of association between atopic asthma and polymorphisms of the histamine H1 receptor, histamine H2 receptor, and histamine N-methyltransferase genes

Histamine functions as one of the major mediators in allergic diseases such as rhinitis, asthma, urticaria, and anaphylaxis when released from mast cells and basophils after cross-linking surface-bound IgE by allergen, The effects of histamine are mediated through three types of receptors, the H1 receptor (HRH1), H2 receptor (HRH2) and H3 receptor (Hill 1990). HRH1 mediates the proinflammatory actions of histamine in the cytokine release and adhesion process (Bachert 1998; Banu and Watanabe 1999), while HRH2 suppresses the production of the Th1-inducing cytokine interleukin-12, resulting in a shift of the Th1/Th2 balance toward Th2 dominance (van der Pouw Kraan et al. 1998). Furthermore, a linkage study identified Chromosome 3p25, where HRH1 is localized, as a candidate gene region for atopy in the Japanese population (Yokouchi et al. 1999).