Cha o 3, a cypress pollen allergen, does not activate basophils in Japanese cypress pollinosis.

Background: In Japan, pollinosis caused by the Japanese cypress (JCy) Chamaecyparis obtusa is among the very common seasonal allergies. In JCy pollinosis, Cha o 1 is the first major allergen, and Cha o 2 is the second major allergen. Recently, Cha o 3 was identified as a new JCy pollen allergen in JCy pollinosis. However, the relative contribution of Cha o 3 to JCy pollinosis compared with that of Cha o 1 and that of Cha o 2 has not been fully elucidated. Objective: This study aimed to clarify the allergenicity of Cha o 3 compared with that of Cha o 1 and Cha o 2 in JCy pollinosis. Methods: We recruited 27 patients with JCy pollinosis and performed the basophil activation test (BAT) with native (n) Cha o 1, Cha o 2, and Cha o 3 purified from JCy pollen. In addition, we a performed JCy-specific IgE suppression test. Results: In the BAT, 26 of 27 patients (96%) and 18 of 27 patients (67%) showed positive basophil activation in response to n Cha o 1 and n Cha o 2, respectively, as judged by CD203c expression. Little CD203c expression in response to n Cha o 3 was seen. The presence of n Cha o 3 marginally reduced the titer levels of JCy-specific IgE. Conclusion: Cha o 3 showed little ability to activate basophils and suppress JCy-specific IgE titers compared with Cha o 1 or Cha o 2 in patients with JCy pollinosis. Thus, Cha o 3 may not be a major allergen in JCy pollinosis.

A highly selective KIT inhibitor MOD000001 suppresses IgE-mediated mast cell activation.

Background: The KIT receptor tyrosine kinase and its ligand, stem cell factor (SCF), control proliferation and survival of mast cells. Thus, targeting KIT signaling may show promise for the treatment of allergic diseases involving mast cells. Recently, we discovered a new compound, MOD000001, as a potential small-molecule KIT kinase inhibitor by using an in silico approach. Objective: We sought to determine whether MOD000001 is highly selective to KIT, inhibits KIT signaling in mast cells, and affects IgE-mediated mast cell activation. Methods: The interaction of MOD000001 with 468 human kinases and its inhibitory activity against KIT were profiled and evaluated by using KINOMEscan (Discover X/Eurofins Corporation, Fremont, Calif) and cell-free kinase assays, respectively. The effects of MOD000001 on SCF-dependent signaling were examined by using primary mouse and human mast cells. The effects of MOD000001 on SCF-induced degranulation and passive cutaneous anaphylaxis reaction were examined in mice. Results: MOD000001 interacted with KIT and inhibited KIT kinase activity with high selectivity. MOD000001 suppressed SCF-induced KIT signaling in mouse and human mast cells and in mice. Passive cutaneous anaphylaxis reaction was suppressed in mice treated with MOD000001 both for a short-term (1 week) and for a long-term (7 weeks). Mice treated with MOD000001 for a long-term, but not for a short-term, showed skin mast cell reduction. Conclusions: MOD000001 is a highly selective KIT inhibitor that can suppress IgE-mediated mast cell activation in vivo. MOD000001 may do so by reducing tissue mast cell numbers or by other unknown mechanisms. The findings suggest potential benefits of MOD000001 for allergic diseases involving IgE-mediated mast cell activation.