MCA SARCOMAS INDUCED IN SCID MICE ARE MORE IMMUNOGENIC THAN MCA SARCOMAS INDUCED IN CONGENIC, IMMUNOCOMPETENT MICE

With the aim of studying possible T-cell mediated selection of the cel ls in growing tumours, 108 mice of the C.B-17 strain, either immunocom petent C.B-17 mice or histocompatible immunodeficient C.B-17 severe co mbined immune deficiency (scid) were treated with 3-methylcholanthrene (MCA) in two different dosages. A total of 51 tumours were obtained, 44 of which were established as uncloned tumour cell lines, and used f or further study. Tumour incidence correlated with carcinogen-dosage i n that more tumours developed in groups treated with a high MCA dose t han in groups treated with a low MCA dose, but not with immune status of the tumour host. No significant difference in the level of MHC clas s I molecule expression was found between the two groups of tumours. T he rate of rejection after transplantation to syngeneic immunocompeten t hosts was significantly higher for the scid tumours than for the non -scid tumours. The authors suggest that this reflects an immunoselecti on performed by T cells in the immunocompetent host in which the tumou r originated, which has eliminated highly immunogenic tumour cells, le aving non-immunogenic tumour cells to grow.