CD1a-positive dendritic cells transport the antigen DNCB intracellularly from the skin to the regional lymph nodes in the induction phase of allergiccontact dermatitis

Dendritic cells are potent stimulators of T cell-mediated immune responses. In contact hypersensitivity reactions in animals dendritic cells have been reported to transport antigens to the regional lymph nodes. In this study we investigated whether skin-derived dendritic cells transport contact anti gens via the afferent lymph in humans. By means of a microsurgical techniqu e lymph cells were collected after painting a defined skin region with a 2% concentration of the sensitizing agent 2,4-dinitrochlorobenzene on the leg of 14 volunteers. There was no significant change in flow, output or compo sition of cells after antigen painting. Using How cytometric analysis we we re able to detect the antigen in CD1a(+) dendritic cells of the afferent ly mph 15-25 h after antigen application. The antigen could only be detected a fter permeabilizing the dendritic cells, indicating that the main part of t he antigen is transported intracellularly and not on the surface of these c ells. Further analysis of cell surface antigens such as CD80, CD86, HLA-DR, CD11a, CD14, CD23, CD25 and CD54 revealed that in the course of cutaneous sensitization the phenotype of the dendritic cells was not altered in the a fferent lymph. These results provide direct evidence that during the induct ion phase of, allergic contact dermatitis in humans antigen-bearing dendrit ic cells internalize the antigen and migrate from the skin via the afferent lymph vessels to the lymph nodes.