 thymectomi adult mice potenti immunosuppress action melphalan l-phenylalanin mustard thymectomi ineffect potenti immunosuppress action melphalan adult cba-p mice challeng a-strain mammari carcinoma transplant true thymectomi perform 2 dai 4 week 7 week prior inject singl dose 15 bodi weight melphalan administ 24 hour prior tumour transplant thymectomi combin multipl dose melphalan tumour transplant find discuss 