Antibodies to tumour eluates react preferentially with non-lymphoid tumours

Rabbit antisera raised against eluates from a murine fibrosarcoma were characterised using a 125I-protein A assay and a wide variety of target cells. The sera bound preferentially to rodent tumours of non-lymphoid origin, whereas monkey and human cells did not react. Murine lymphoid cells and macrophages (normal or transformed) and normal liver and kidney cells all bound low amounts of the antibody, while embryonic cells were intermediate in reactivity. Target cell treatments indicated that the surface antigens being detected were sensitive to proteolysis and calcium depletion. In addition actively growing cells bound more antibody than resting cells. Double binding assays with sera specific for plasma membrane components suggested the eluate antigens may play a structural role. Immunofluorescent studies demonstrated that surface antigens detected by the antisera capped and were lost and this was followed by synthesis and surface re-expression. Sera such as these, which can distinguish between normal and malignant cells in the rodent, have obvious applications in many aspects of tumour-related investigations.