CONTROL MECHANISMS OF CELL-MEDIATED REACTIONS

One of the most relevant aspects of tumor adoptive immunotherapy is pr ovided by clinical trials on transfer of cytotoxic cells (LAK and TIL) . However, LAK cell therapy is effective in a small number (16-22%) of only certain tumors, while therapy with TIL cells is efficient in abo ut 40% of melanomas. Several possibilities have been raised to explain the low efficacy of cytotoxic cells in tumor therapy, amongst which a re the poor immunogenicity of tumor and tumor-induced immunodepression . Furthermore, the possibility that cytotoxic cells do not reach the t umor site in adequate numbers has to be considered. We have developed an experimental system to study the ability of antigen-specific T cell s to reach the target antigen in the tissues. The results obtained dem onstrate that gamma delta cells and IL-4 are required to allow tissue localization of antigen-specific alpha beta cells, thus indicating tha t their ability to exert certain effector functions requires cooperati on by other cell types. These results may be relevant to the understan ding of the mechanisms leading to localization of immunologically acti ve cells at a tumor site.