Tumour‐specific immunity against spontneous rat tumours

The antigenicities of two spontaneously developing rat tumours, a reticulum cell sarcoma and a squamous cell carcinoma, have been studied. With the reticulum cell sarcoma, no immunity could be demonstrated following either destruction of tumour grafts or implantation of heavitly irradiated (14,500 R) tumour into isogeneic hosts. Destruction of subcutaneous grafts by ligation oftheir blood supply proved to be effective for inducing immunity to the squamous cell carcinoma. In contrast, implantation of heavily irradiated tumour was completely inefective in producing resistance. The level of immunity imduced following destruction of subcutaneous grafts fo the squamous cell varcinoma varied markedly and this was ascribed to the tendency of the tumour to metastasize. Moreover, in some instances, rats immune to subcutaneous challenges with this tumour eventually developed lung metastases. Whils the prsent studies demonstrate the antigenicity of a spontaneously arising tumour, th level of resistance which can be produced is much lower than that detected with carcinogen‐induced tumours. Furthermore, immunological control of tumour metastases appears to be a problem not previously encountered with carcinogen‐induced tumours and this may also reflect differences in the antigenicities of the two tumour types.