Correlation of immune response with clinical stage in Lewis lung tumor-bearing mice

The effect of Lewis lung tumor growth in mice on the induction of primary immune response to SRBC, was investigated by PFC assay for measuring antibody activity and by footpad test as a correlate for delayed type hypersensitivity reactions. With the appearance of micrometastases in the lungs there was a decline in the humoral and cellular immune response to the SRBC. An increase of number and size of metastases in the lungs led to a further depression of the immune reactivity. Since the reduction of general immune response in mice bearing this tumor is not due to a direct influence of tumor cells, it might be assumed that suppressor cells or factors, are actively abrogating the general and also the tumor directed immune reactions.