David P. Carbone

IMMUNOLOGIC DYSFUNCTION IN CANCER

The interactions between the tumor and its host are complex, and many aspects of the immune system appear to be adversely affected directly or indirectly by the presence of the tumor. Virtually all of the processes involved in immune induction and action have been implicated in the observed deficient response in tumor-bearing patients. Improved understanding and molecular analysis of the mechanisms underlying the escape of tumors from immune surveillance may lead to the development of novel strategies for the prevention of T-cell immunosuppression in cancer patients, the development of novel immunotherapeutic strategies, and potentially prevention of tumor progression or development.

In vivo cytotoxicity assay for assessing immunity

A rapid, quantitative, in vivo assay of cytotoxic responses would facilitate experimental evaluation of the potency of novel vaccine strategies. We have developed an in vivo cytotoxicity assay in which target cells expressing a luciferase reporter gene are implanted as monolayers on polystyrene disks onto the muscle tissue of mice. The luciferase activity retrievable from the adjacent tissue is used as an index of cytotoxicity. Implantation of B16 or NIH/3T3 cells expression the beta-galactosidase gene indicated that the target cells migrated to the muscle tissue from plastic within 4 h and then remained localized in the area of the disk. The amounts of luciferase retrievable from the adjacent tissue a few days post implantation readily detected the immune response induced by allo-immunization of fibroblasts or by production of interleukin-4 by tumor cells co-mixed with implanted reporter cells. Histologic analysis showed a correlation between the amount of luciferase retrieved and the number of viable target cells at the implantation site. Recruitment of immune effector cells which may be responsible for target cell death and luciferase elimination could be readily visualized. This simple cytotoxicity assay can be used as an in vivo assay of the net effect of cytotoxic immune responses.