Control mechanisms of cell-mediated reactions

One of the most relevant aspects of tumor adoptive immunotherapy is provided by clinical trails 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 about 40% of melanomas. Several possibilities have been raised to explain the low efficacy of cytotoxic cells in tumor therapy, amongst which are the poor immunogenicity of tumor and tumor-induced immunodepression. Furthermore, the possibility that cytotoxic cells do not reach the tumor site in adequate numbers has to be considered. We have developed an experimental system to study the ability of antigen-specific T cells to reach the target antigen in the tissues. The results obtained demonstrate that gamma delta cells and IL-4 are required to allow tissue localization of antigen-specific alpha beta cells, thus indicating that their ability to exert certain effect or functions requires cooperation by other cells types. These results may be relevant to the understanding of the mechanisms leading to localization of immunologically active cells at a tumor site.