[1] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, Leukocyte Biol Sect, London SW7 2AZ, England
[2] Natl Univ Singapore, Ctr Life Sci, Immunol Programme, Singapore 117548, Singapore
[3] Royal Brompton Hosp, Dept Resp Paediat, London SW3 6LY, England
[4] Univ London Imperial Coll Sci Technol & Med, Natl Heart & Lung Inst, London, England
[5] Barts & London Queen Marys Sch Med & Dent, Blizard Inst, Ctr Primary Care & Publ Hlth, London, England