[1] Dept Biochem, MRC Immunochem Unit, South Parks Rd, Oxford OX1 3QU, England
[2] ICI Pharmaceut Div Ltd, Alderley Pk, Macclesfield SK10 4TG, Cheshire, England
[3] Dept Biochem, Formerly MRC Immunochem Unit, South Parks Rd, Oxford OX1 3QU, England
[4] Formerly MRC Immunochem Unit, Oxford, England
[5] 11647 Brook Lane, Hayward, WI 54843 USA
[6] Dept Pharmacol, Mansfield Rd, Oxford OX1 3QT, England
[7] Univ Oxford, Green Templeton Coll, Woodstock Rd, Oxford OX2 6HG, England