Immature human monocyte-derived dendritic cells migrate rapidly to draining lymph nodes after intradermal injection for melanoma immunotherapy.

Injected antigen-loaded immature monocyte-derived dendritic cells (DCs) may be incapable of migrating from skin to draining lymph nodes for antigen presentation. The in vivo migratory capacity of intradermally administered immature monocyte-derived DCs was therefore investigated during a phase I/II clinical trial for metastatic melanoma. DCs cultured from adherent monocytes in the presence of autologous serum, granulocyte-macrophage colony stimulating factor and interleukin-4 were pulsed with antigen and labelled with technetium-99m hexamethylpropylene-amineoxime (99mTc-HMPAO) ex vivo, then injected intradermally. A 99mTc-HMPAO control containing an equivalent amount of radioactivity was injected into the opposite thigh. The pelvis was then imaged with a gamma camera. The DCs were characterized as immature by functional and phenotypic analysis. Labelled DCs travelled to the draining inguinal lymph nodes within 10 min, and the draining lymph nodes were clearly outlined up to 4 h after injection. Free NmTc outlined draining lymph nodes after 10 min but was cleared from the nodes within 1 h. Thus, immature human monocyte-derived DCs migrate rapidly to and remain in draining lymph nodes after intradermal injection for immunotherapy.