The dynamics of the T-cell antitumor response: chemokine-secreting dendritic cells can prime tumor-reactive T cells extranodally.

Direct administration of dendritic cells (DCs) genetically modified to express secondary lymphoid tissue chemokine (SLC) into growing B16 melanoma could result in a substantial, sustained influx of T cells within the mass with only a transient increase in T-cell numbers in the draining lymph node (DLN). DCs were retained at the tumor site with only a very small percentage trafficking to the DLN. The T cells infiltrating the tumor mass expressed the activation marker CD25 within 24 h and developed IFN-gamma-secreting function within 7 days as tumor growth was inhibited. Similar results were obtained in lymphotoxin alpha-/- mice, which lacked peripheral lymph nodes. Our data demonstrate that effective T-cell priming can occur extranodally and result in measurable antitumor effects in vivo.