<qa>  What is the preventive treatment of the GvHa?- without GvHa at the time of the inclusion or GvHa II controlled by Corticoids 1mg Kg but corticosteroids on decrease or cyclosporine only. A possible treatment by monoclonal antibody anti r-IL2 LEUCOTAC must have been interrupted for at least 8 days. The preventive treatment of the GvHa by cyclosporine or mycophenolate mofetil is compatible with the study 