The targeted delivery of Ags to dendritic cell (DCs) in vivo greatly improves the efficiency of Ag presentation to T cells and allows an analysis of receptor function. To evaluate the function of Langerin/CD207, a receptor expressed by subsets of DCs that frequently coexpress the DEC205/CD205 receptor, we genetically introduced OVA into the C terminus of anti-receptor Ab H chains. Taking advantage of the new L31 mAb to the extracellular domain of mouse Langerin, we find that the hybrid Ab targets appropriate DC subsets in draining lymph nodes and spleen. OVA is then presented efficiently to CD8+ and CD4+ T cells in vivo, which undergo 4–8 cycles of division in 3 days. Peptide MHC I and II complexes persist for days. Dose response studies indicate only modest differences between Langerin and DEC receptors in these functions. Thus, Langerin effectively mediates Ag presentation.

Dendritic cells (DCs) are strategically positioned to take up antigens and initiate adaptive immunity. One DC subset expresses CD8␣␣ in mice and is specialized to capture dying cells and process antigens for MHC class I ''cross-presentation.'' Because CD8 ؉ DCs also express DEC205/CD205, which is localized to splenic T cell regions, it is thought that CD8 ؉ DCs also are restricted to T zones. Here, we used a new antibody to Langerin/CD207, which colabels isolated CD8 ؉ CD205 ؉ DCs, to immunolabel spleen sections. The mAb labeled discrete cells with high levels of CD11c and CD8. Surprisingly most CD207 ؉ profiles were in marginal zones surrounding splenic white pulp nodules, and only smaller numbers were in T cell areas, where CD205 colabeling was noted. Despite a marginal zone location, CD207 ؉ DCs lacked identifying molecules for 3 different types of macrophages, localized in proximity and, in contrast to macrophages, marginal zone DCs were poor scavengers of soluble and particulate substrates. After stimulation with microbial agonists, Langerin expression disappeared from the marginal zone at 6 -12 h, but was greatly expanded in the T cell areas, and by 24 -48 h, Langerin expression disappeared. Therefore, anti-Langerin antibodies localize a majority of CD8 ؉ DCs to non-T cell regions of mouse spleen, where they are distinct from adjacent macrophages.

ϩ DCs are superior cells for the cross-presentation of Ags on MHC class I molecules (5-7). Molecular mechanisms for these distinct functions are starting to be identified, e.g., CD8␣ϩ DCs express higher levels of mRNA transcripts and proteins involved in the MHC class I processing pathway (7).Apoptotic cells are generated continually in mammals and other species, and cell death is increased further during embryo development, tissue remodeling, and inflammation. Potentially harmful cells that are eliminated by apoptosis include self-reactive T and B cells, tumor cells, and cells infected with viruses and some bacteria. Engulfment of apoptotic cells in some instances suppresses production of inflammatory cytokines from activated macrophages (8). When dying cells are engulfed by DCs in the steady state in the absence of infection or immunological adjuvants, Ag-specific tolerance to Ags in the dying cells can be induced (3). In contrast, if mice are given dying cells with adjuvants, Ag-specific T cell responses develop (3, 9). Analyses of genetically modified mice have shown that increased accumulation of apoptotic cells induces the development of autoimmune diseases (10 -12). Thus, accumulating evidence indicates that the uptake of apoptotic cells is not only a clearance mechanism, but is also capable of suppressing inflammation and modulating immune responses from Ag-specific tolerance to resistance (13).In vitro studies indicate that many receptors can be involved in the uptake of dying cells by macrophages, including scavenger receptors, the phosphatidylserine receptor, integrins, CD14, C1q, C1qR,. Recently, the T cell Ig and mucin domain-containing molecules, Tim-1 and Tim-4, The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked advertisement in accordance with 18 U.S.C. Section 1734 solely to indicate this fact. 3 Abbreviations used in this paper: DC, dendritic cell; DAP10, DNAX activation protein 10 kDa; DAP12, DNAX activation protein 12 kDa; Flt3L, Fms-like tyrosine kinase 3 ligand; HEK, human embryonic kidney; Mertk, Mer tyrosine kinase; PI, propidium iodide; poly(I:C), polyinosine-polycytidylic acid; Trem, triggering receptor expressed on myeloid cells; Treml4, Trem-like 4; SIGN-R1, specific intracellular adhesion molecule-grabbing nonintegrin receptor 1.

Tensional homeostasis is crucial for organ and tissue development, including the establishment of morphological and functional properties. Skin plays essential roles in waterproofing, cushioning and protecting deeper tissues by forming internal tension-distribution patterns, which involves aligning various cells, appendages and extracellular matrices (ECMs). The balance of traction force is thought to contribute to the formation of strong and pliable physical structures that maintain their integrity and flexibility. Here, by using a human skin equivalent (HSE), the horizontal tension-force balance of the dermal layer was found to clearly improve HSE characteristics, such as the physical relationship between cells and the ECM. The tension also promoted skin homeostasis through the activation of mechano-sensitive molecules such as ROCK and MRTF-A, and these results compared favourably to what was observed in tension-released models. Tension-induced HSE will contribute to analyze skin physiological functions regulated by tensional homeostasis as an alternative animal model.