Immune-mediated antitumor effect of a transplanted lymph node.

Lymph node (LN) transplantation is a recognized method for reconstruction of the lymphatic system and is used in the clinical setting to treat lymphedema. However, it is unclear whether transplanted LNs contribute to immune surveillance. In our study, we investigated whether a single transplanted non-vascularized LN, defined as a tumor-draining transplanted lymph node (TDTLN), could exert an immune-mediated antitumor effect. LN and lung metastases and primary tumor enlargement were evaluated in mice that were inoculated with B16-F10-luc2 melanoma cells in a hind limb footpad without (group 1) and with (group 2) popliteal lymph node (PLN) resection and in mice that underwent LN transplantation after PLN resection (group 3). The function of a TDTLN (group 3) and a tumor-draining popliteal lymph node (TDPLN; group 1) was evaluated in the context of cancer. LN and lung metastases were significantly aggravated by PLN resection but were significantly decreased by LN transplantation. Immunohistochemistry showed that the TDTLNs retained T-cells and B-cells and fluorescence-activated cell sorting analysis confirmed expansion of lymphocytes in these nodes; however, the degree of expansion in TDTLNs was different from that in TDPLNs. Expression of cytokines associated with immunostimulation was confirmed in the TDTLNs as well as in the TDPLNs. One of the differences in the immune-mediated antitumor effect of the TDPLNs and TDTLNs was ascribed to a difference in the site of lymphocyte homing to peripheral LNs through high endothelial venules. Non-vascularized LN transplantation had an immune-mediated antitumor effect.