1. From the Institut National de la Santé et de la Recherche Médicale, Unit 543 (C.C., M.R., A. Pezard) and Unit 689 (S.P., T.S., B.E., R.M., AT., Z.M.), Université Pierre et Marie Curie, Paris 6 (C.C.), Paris, France; and Serono Pharmaceutical Research Institute, Geneva, Switzerland (A. Proudfoot).