[1] Inst Psychiat, Sect Clin Neuropharmacol, Therapeut Res Grp, London SE5 8AF, England
[2] Guys Kings St Thomas Sch Med, Dept Gastroenterol, London, England
[3] Guys Kings St Thomas Sch Med, Dept Immunol, London, England
[4] Hlth Protect Agcy, Stat Unit, London, England
[5] Royal Coll Physicians, London NW1 4LE, England
[6] Univ London Imperial Coll Sci Technol & Med, Northwick Pk Hosp, Dept Histopathol, London, England
[7] Univ London Imperial Coll Sci Technol & Med, St Marks Hosp, Dept Histopathol, London, England
[8] Univ Hertfordshire, Hatfield AL10 9AB, Herts, England