Considering two previous reports which showed that FcεRI-β protein has a role as a stabilizer of FcεRI expression (Donnadieu et al., 2000), and that the FcεRI-βγ complex supports FcεRI-α insertion to ER and promotes cell-surface expression (Fiebiger et al., 2005), we supposed that an increased FcεRI-β protein expression in response to monomeric IgE contributes to allergic reaction through the FcεRI stabilizing role. Here, MS4A2 is linked to allergic disease.