Monocyte Chemoattractant Protein Inhibits the Generation of Tumor-reactive T Cells

The adoptive transfer of tumor-sensitized T cells can eradicate disseminated malignancy in murine animal models. T cells must be sensitized to tumor antigens in vivo to acquire antitumor reactivity. T-cell sensitization has been demonstrated to be dependent on host antigen-presenting cells. Tumor-associated macrophages are a heterogeneous population of cells that may have both inhibitory and stimulatory influences on the sensitization of naive T cells. Here we demonstrate that a weakly immunogenic tumor, the MCA 205 sarcoma, produces substantial amounts of murine monocyte chemoattractant protein 1 (MCP-1). Neutralization of MCP-1 during in vivo T-cell sensitization resulted in T cells that possessed enhanced therapeutic activity against established pulmonary metastases. These T cells sensitized during MCP-1 depletion also exhibited enhanced production of IFN-γ upon recognition of tumor targets. These results demonstrate that MCP-1 can have a potent inhibitory influence on the development of tumor-reactive T cells.