Effect of Thymectomy on Transplantation Resistance induced by Polyoma Tumour Homografts

Abstract

POLYOMA virus will induce neoplasms in most strains of newborn mice but not usually in mice older than 2 weeks^1,2. Adult mice infected with polyoma virus are relatively more resistant to challenge of syngeneic polyoma-type tumours³. Such resistance can also be induced by homografts of polyoma tumours⁴. This resistance is not dependent on circulating viral antibodies and can apparently be transferred to normal recipients by lymphoid cells from immunized mice. To interpret these findings, Habel⁵ and Sjögren et al.⁶ proposed that polyoma virus transforms normal cells to neoplastic cells in the newborn and in the adult mouse, and that the transformed cells now contain a new foreign cell antigen which will provoke an immune response in the adult but not in the newborn animal. Thus, ordinarily, neoplasms will arise in newborn animals, whereas adult animals are capable of rejecting tumour cells containing foreign antigen. This tumour antigen is apparently common for most polyoma tumours induced by the same strain of virus⁷. This concept is supported by the finding that thymectomy during the immediate postnatal period—known to effect maturation of immunological faculty–can alter the course of polyoma virus oncogenesis. Thymectomy at 3 days of age rendered normally highly resistant (C57BL) mice susceptible to the oncogenic action of polyoma virus⁸. The same effect was found when the virus was injected into mice 1 month old⁹. Mice thymectomized when 3 days old and then infected with polyoma virus were unable to develop transplantation resistance against a challenge of syngeneic polyoma tumour cells¹⁰. Additional evidence is now reported that C57BL mice, thymectomized at 3 days of age and then immunized with homografts of polyoma tumour cells when 1 month old, are unable to develop resistance against challenge by syngeneic polyoma tumour cells.