1. 1��� Wills-Karp M , Santeliz J , Karp CL. The germless theory of allergic disease: revisiting the hygiene hypothesis. Nat Rev Immunol 2001; 1:69���75.
2. 2��� Crabbe PA , Nash DR , Bazin H , Eyssen H , Heremans JF. Immunohistochemical observations on lymphoid tissues from conventional and germ-free mice. Lab Invest 1970; 22:448���57.
3. 3��� Sudo N , Sawamura S , Tanaka K , Aiba Y , Kubo C , Koga Y. The requirement of intestinal bacterial flora for the development of an IgE production system fully susceptible to oral tolerance induction. J Immunol 1997; 159:1739���45.
4. 4��� Bj��rkst��n B. Perinatal events in relation to sensitization in the human. Am J Respir Crit Care Med 2000; 162:S105���7.
5. 5��� Gerrard JW , Geddes CA , Reggin PL , Gerrard CD , Horne S. Serum IgE levels in white and metis communities in Saskatchewan. Ann Allergy 1976; 37:91���100.