OBJECTIVETo retrospectively analyze the quantity and status of the tumor infiltrating regulatory T lymphocytes in breast cancer and the draining lymph nodes, and to elucidate the clinical pathologic significance.

METHODSSeventy-four breast cancer samples with excised axillary lymph nodes were typed and staged histopathologically. The regulatory T lymphocytes were labeled by immunohistochemistry using EnVision method with the monoclonal antibodies against CD25 and Foxp3, and the immunophenotype was analyzed. In addition, the expression of IFN-γ, IL-10 and TGF-β1 mRNA in lymphocytes of lymph nodes draining the tumors was detected by in situ hybridization with the corresponding specific oligo nucleaic acid probes.

RESULTSThe number of CD25(+)Foxp3(+) T cells infiltrating the interstitium was much higher than that in the parenchymal tissue of the cancer. In the tumor draining lymph nodes, CD25(+) cells and Foxp3(+) cells were predominantly distributed in the paracortex with a proliferative pattern. TGF-β1, INF-γ and IL-10 mRNA positive cells showed a similar distribution pattern in the draining lymph nodes. Among the 39 cases with metastatic disease, the lymph nodes with metastases showed a much higher number of CD25(+)Foxp3(+) cells than that without metastases (23.5 vs 17.3 and 23.8 vs 15.5; P < 0.05). However, there was no difference in the density of Foxp3(+)CD25(+) cells in the draining lymph nodes between the death and survival groups (P > 0.05). Cytokine expression of TGF-β1, IL-10 and IFN-γ mRNA in the lymphocytes of draining lymph nodes in 24 cases showed that there were more IL-10 mRNA positive cells in the dead patients than that in the survived patients. A similar trend was observed for TGF-β1 mRNA positive cells but the difference was not statistically significant (P > 0.05). The expression rate of TGF-β1 and IL-10 mRNA in the draining lymph nodes was proportional to that of CD25(+) and Foxp3(+) cells (P < 0.05), and the expression of TGF-β1 positive cells was also proportional to that of IL-10 mRNA positive cells (P < 0.01). The expression of IFN-γ mRNA among these groups showed no significance (P > 0.05).

CONCLUSIONSRegulatory T cells may play important roles in inhibiting the host antitumor immunity, and the presence of increased regulatory T cells and Th2-secreting cells in paracortex with a proliferative pattern in the tumor draining lymph nodes implies that the paracortical proliferation of draining lymph nodes may not reflect positive antitumor effects.