Profile of regulatory T cells and interferon γ secretion in the tumor-draining lymph node from mouse Hepa1–6 cells

BackgroundThe tumor-draining lymph node (TDLN) is the critical and initial site of the immune decision made between activation and tolerance to tumor antigens. Tumor-reactive lymphadenopathy in TDLN has been observed for decades, but the profiles of immune regulation in these nodes remain unclear.Materials and methodsBoth regulatory T cells (Tregs) and effector T cells were examined using 6 × 105 Hepa1–6 hepatocellular carcinoma cells implanted in footpads of syngeneic C57BL/6J mice, which formed TDLN. FOXP3+ Tregs and CD8+ T cells in TDLN were detected by immunohistochemical staining. The frequency of CD4+FOXP3+ T cells and FOXP3 mRNA expression were determined by flow cytometry and real-time quantitative polymerase chain reaction. The interferon γ secretion ability of CD8+ T cells in TDLN was measured by enzyme-linked immunospot technique.ResultsThere was significant expansion of Tregs and CD8+ T cells in the tumor-draining popliteal lymph node compared with nondraining popliteal lymph node and spleen in the same mouse. Tregs were diffusely distributed in the CD8+ T cell compartment. The CD8+ T cells primed in TDLN showed a strong ability of interferon γ secretion via in vitro stimulation.ConclusionsThese findings support the notion that Tregs suppress CD8+ T cells by secreting cytokines such as transforming growth factor β and interleukin 10, but do not make CD8+ T cells lose function in the TDLN. Deletion of Tregs at the secondary lymphoid organs could be crucial for the establishment of a tumor-specific immunotherapy.