Human Cutaneous Dendritic Cells Migrate Through Dermal Lymphatic Vessels in a Skin Organ Culture Model

The capacity to migrate from peripheral tissues, where antigen is encountered, to lymphoid organs, where the primary immune response is initiated, is crucial to the immunogenic function of dendritic cells (DC). The skin is a suitable tissue to study migration. DC were observed to gather in distinct nonrandom arrays (“cords”) in the dermis upon culture of murine whole skin explants. It is assumed that cords represent lymphatic vessels. Using a similar organ culture model with human split-thickness skin explants, we investigated migration pathways in human skin.We made the following observations. 1) Spontaneous emigration of Langerhans cells took place in skin cultured for 1–3 d. Nonrandom distribution patterns of strongly major histocompatibility complex class II-expressing DC (cords) occurred in cultured dermis. A variable, yet high (>50%) percentage of these DC coexpressed the Birbeck granule-associated antigen “Lag” Ultrastructurally, the cells corresponded to mature DC. 2) Electron microscopy proved that the dermal structures harboring the accumulations of DC (i.e., cords) were typical lymph vessels. Moreover, markers for blood endothelia (monoclonal antibody PAL-E, Factor VIII-related antigen) and markers for cords (strong major histocompatibility complex class II expression on nonrandomly arranged, hairy-appearing cells) were expressed in a mutually exclusive pattern. 3) On epidermal sheets we failed to detect gross changes in the levels of expression of adhesion molecules (CD44, CD54/ICAM-1, E-cadherin) on keratinocytes in the course of the culture period.The reactivity of a part of the DC in the dermal cords with Birbeck granule-specific monoclonal antibody “Lag” suggests that the migratory population is composed of both epidermal Langerhans cells and dermal DC. We conclude that this organ culture model may prove helpful in resolving pathways and mechanisms of DC migration

Entry Into Afferent Lymphatics and Maturation In Situ of Migrating Murine Cutaneous Dendritic Cells

An important property of dendritic cells (DC), which contributes crucially to their strong immunogenic function, is their capacity to migrate from sites of antigen capture to the draining lymphoid organs. Here we studied in detail the migratory pathway and the differentiation of DC during migration in a skin organ culture model and, for comparison, in the conventional contact hypersensitivity system. We report several observations on the capacity of cutaneous DC to migrate in mouse ear skin. (i) Upon application of contact allergens in vivo the density of Langerhans cells in epidermal sheets decreased, as determined by immunostaining for major histocompatibility complex class II, ADPase, F4/80, CD11b, CD32, NLDC-145/DEC-205, and the cytoskeleton protein vimentin. Evaluation was performed by computer assisted morphometry. (ii) Chemically related nonsensitizing or tolerizing compounds left the density of Langerhans cells unchanged. (iii) Immunohistochemical double-staining of dermal sheets from skin organ cultures for major histocompatibility complex class II and CD54 excluded blood vessels as a cutaneous pathway of DC migration. (iv) Electron microscopy of organ cultures revealed dermal accumulations of DC (including Birbeck granule containing Langerhans cells) within typical lymphatic vessels. (v) Populations of migrating DC in organ cultures upregulated markers of maturity (the antigen recognized by monoclonal antibody 2A1, CD86), but retained indicators of immaturity (invariant chain, residual antigen processing function). These data provide additional evidence that during both the induction of contact hypersensitivity and in skin organ culture, Langerhans cells physically leave the epidermis. Both Langerhans cells and dermal DC enter lymphatic vessels. DC mature while they migrate through the skin

A fusion inhibitor prevents spread of immunodeficiency viruses, but not activation of virus-specific T cells, by dendritic cells

Dendritic cells (DCs) play a key role in innate immune responses, and their interactions with T cells are critical for the induction of adaptive immunity. However, immunodeficiency viruses are efficiently captured by DCs and can be transmitted to and amplified in CD4+ T cells, with potentially deleterious effects on the induction of immune responses. In DC-T-cell cocultures, contact with CD4+, not CD8+, T cells preferentially facilitated virus movement to and release at immature and mature DC-T-cell contact sites. This occurred within 5 min of DC-T-cell contact. While the fusion inhibitor T-1249 did not prevent virus capture by DCs or the release of viruses at the DC-T-cell contact points, it readily blocked virus transfer to and amplification in CD4+ T cells. Higher doses of T-1249 were needed to block the more robust replication driven by mature DCs. Virus accumulated in DCs within T-1249-treated cocultures but these DCs were actually less infectious than DCs isolated from untreated cocultures. Importantly, T-1249 did not interfere with the stimulation of virus-specific CD4+ and CD8+ T-cell responses when present during virus-loading of DCs or for the time of the DC-T-cell coculture. These results provide clues to identifying strategies to prevent DC-driven virus amplification in CD4+ T cells while maintaining virus-specific immunity, an objective critical in the development of microbicides and therapeutic vaccines

Disruption of the langerin/CD207 Gene Abolishes Birbeck Granules without a Marked Loss of Langerhans Cell Function

Langerin is a C-type lectin expressed by a subset of dendritic leukocytes, the Langerhans cells (LC). Langerin is a cell surface receptor that induces the formation of an LC-specific organelle, the Birbeck granule (BG). We generated a langerin(−)(/)(−) mouse on a C57BL/6 background which did not display any macroscopic aberrant development. In the absence of langerin, LC were detected in normal numbers in the epidermis but the cells lacked BG. LC of langerin(−)(/)(−) mice did not present other phenotypic alterations compared to wild-type littermates. Functionally, the langerin(−)(/)(−) LC were able to capture antigen, to migrate towards skin draining lymph nodes, and to undergo phenotypic maturation. In addition, langerin(−)(/)(−) mice were not impaired in their capacity to process native OVA protein for I-A(b)-restricted presentation to CD4(+) T lymphocytes or for H-2K(b)-restricted cross-presentation to CD8(+) T lymphocytes. langerin(−)(/)(−) mice inoculated with mannosylated or skin-tropic microorganisms did not display an altered pathogen susceptibility. Finally, chemical mutagenesis resulted in a similar rate of skin tumor development in langerin(−)(/)(−) and wild-type mice. Overall, our data indicate that langerin and BG are dispensable for a number of LC functions. The langerin(−)(/)(−) C57BL/6 mouse should be a valuable model for further functional exploration of langerin and the role of BG