1. Cellular Biology Laboratory (H.W., D.A., H.O., M.M., K.Sai., Y.T., T.K., I.T., T.H., G.C., S.O., K.W., T.Y., H.A.), Graduate School of Agricultural Science, Tohoku University, Sendai 981-8555, Japan
2. Field Science Center (H.O.), Yakumo Experimental Farm, School of Veterinary Medicine, Kitasato University futami-gun, Hokkaido 049-3121, Japan
3. Animal Science (K.Sat.), Department of Biological Production, Tokyo University of Agriculture and Technology, Fuchu-shi, Tokyo 183-8509, Japan
4. Laboratory for Epithelial Immunobiology Research Center for Allergy and Immunology (T.K.), RIKEN, Yokohama-shi, Kanagawa 230-0045, Japan
5. Institute of Biological, Environmental and Rural Sciences (M.T.R.), Aberystwyth University, Cardiganshire, SY23 3AL, United Kingdom