[Effect of modification of host immune activity on radiation therapy]

In this previous meeting, author reported that specific anti-tumor T cells, perhaps helper T cells, are induced in host mice after local irradiation to tumor. Immunostimulators were used following local irradiation to tumor. However, because suppressor T cells were also stimulated by these drugs, cyclophosphamide was used to suppress suppressor T cells. The results indicate that the combined use of immunostimulator and suppressor of suppressor T cells is very effective in radiation therapy. In the combined use of these drugs, the following three factors are very important: 1) whether the drug is administered before or after radiation, 2) the time interval between administrations of immunostimulator and suppressor T cells and local irradiation, and 3) dosage. Good effects were not obtained when dosage exceeded appropriate levels. The relationships among these factors are critical.