Langerhans cells, a subset of skin dendritic cells in the epidermis, survey peripheral tissue for invading pathogens. In recent
functional studies it was proven that Langerhans cells can present exogenous antigen not merely on major histocompatibility
complexes (MHC)-class II molecules to CD4
+ T cells, but also on MHC-class I molecules to CD8
+ T cells. Immune responses against topically applied antigen could be measured in skin-draining lymph nodes. Skin barrier
disruption or co-application of adjuvants was required for maximal induction of T cell responses. Cytotoxic T cells induced
by topically applied antigen inhibited tumor growth in vivo, thus underlining the potential of Langerhans cells for immunotherapy.
Here we review recent work and report novel observations relating to the potential use of Langerhans cells for immunotherapy.
We investigated the potential of epicutaneous immunization strategies in which resident skin dendritic cells are loaded with
tumor antigen in situ. This contrasts with current clinical approaches, where dendritic cells generated from progenitors in
blood are loaded with tumor antigen ex vivo before injection into cancer patients. In the current study, we applied either
fluorescently labeled protein antigen or targeting antibodies against DEC-205/CD205 and langerin/CD207 topically onto barrier-disrupted
skin and examined antigen capture and transport by Langerhans cells. Protein antigen could be detected in Langerhans cells
in situ, and they were the main skin dendritic cell subset transporting antigen during emigration from skin explants. Potent
in vivo proliferative responses of CD4
+ and CD8
+ T cells were measured after epicutaneous immunization with low amounts of protein antigen. Targeting antibodies were mainly
transported by langerin
+ migratory dendritic cells of which the majority represented migratory Langerhans cells and a smaller subset the new langerin
+ dermal dendritic cell population located in the upper dermis. The preferential capture of topically applied antigen by Langerhans
cells and their ability to induce potent CD4
+ and CD8
+ T cell responses emphasizes their potential for epicutaneous immunization strategies.
Keywords Dendritic cells - Migration - Vaccination - Epicutaneous - Langerhans cells - Transcutaneous
This article is a symposium paper from the conference “Immunotherapy—From Basic Research to Clinical Applications,” Symposium
of the Collaborative Research Center (SFB) 685, held in Tübingen, Germany, 6–7 March 2008.