ABSTRACT
The ability of tumor cells to replicate within a host despite demonstrable tumor-specific cell-mediated immunity remains a major paradox to immunologists. This chapter describes an animal tumor model, a fibrosarcoma in strain 13 guinea pigs, used to investigate tumor escape mechanisms. It explains a model system to study tumor-escape mechanisms in the guinea pig. Lymphocyte transformation to mitogens, phytohemagglutinin (PHA) and pokeweed mitogen, was used to monitor overall immune function during tumor growth. Comparison of dinitrofluorobenzene immunization and tumor induction also suggests a relationship between degree and persistence of antigen exposure and persistence of both Fraction 4 elevation and lymphocyte suppression. The inability of lymphocyte cultures from tumorous animals to regain a normal PHA response after extensive washing suggested that the suppressive factor in the plasma might be tightly bound by the cells. The suppressive factor affects lymphocytes from both normal and tumorous animals.
