[1] Univ Basel Hosp, CH-4031 Basel, Switzerland
[2] Univ British Columbia, Vancouver, BC V5Z 1M9, Canada
[3] Johns Hopkins Univ, Baltimore, MD USA
[4] Univ Toronto, Toronto, ON, Canada
[5] McGill Univ, Montreal, PQ, Canada
[6] Vrije Univ Amsterdam Med Ctr, Amsterdam, Netherlands
[7] Genentech Inc, San Francisco, CA 94080 USA
[8] F Hoffmann La Roche Ltd, Basel, Switzerland
[9] Univ Calif San Francisco, San Francisco, CA 94143 USA