Sentinel node mapping identifies vaccine-draining lymph nodes with tumor-specific immunological activity

Background: Adoptive immunotherapy (AIT) with 4T07-IL2 vaccine-draining lymph node (DLN) cells induced regression of established 4T07 mammary carcinomas, but contralateral non-DLN were inactive. These experiments were performed to determine whether mapping with isosulfan blue (IB), as described for identification of sentinel nodes, would identify vaccine-DLN with antitumor activity. Methods: Ten days after vaccination with 4T07-IL-2, .1 ml of 1% IB was injected into the vaccination site (footpads or flanks). After 3 minutes, mice were euthanized, and the blue-stained nodes were collected. With flank vaccination, IB identified both an inguinal and an axillary node. We also collected DLNs blindly in mice not receiving IB dye. DLN cell suspensions were then activated with bryostatin 1, ionomycin, and IL-2, expanded in culture, and adoptively transferred to mice bearing established 4T07 flank tumors. Results: Complete tumor regression occurred in nearly all mice treated with popliteal or inguinal DLNs collected with or without IB. IB-stained axillary DLNs cured 100% of tumor-bearing mice, whereas none of the mice treated with blindly collected axillary DLNs were cured. Conclusion: We have shown that IB identifies immunologically active DLNs, does not interfere with expansion of lymphocytes in vitro, and, more importantly, has no detrimental effect on the ability of lymphocytes to induce tumor regression in vivo. For axillary DLNs, use of IB mapping identified immunologically active lymph nodes that could not otherwise be found.