It is made of a single polypeptide chain and contains 10 lectin domains, which is a deviation from the eight lectin domains of the MMR family. Named from the first observations of its abundant expression on DCs and thymic epithelial cells in mice using the rat monoclonal antibody non-lymphoid dendritic cells (NLDC)-145 [73,74], DEC-205 has a more diverse distribution. B cells from various sources such as spleen, lymph node and peritoneal exudates express

DEC-205, but at a much lower level than on DCs [75]. Immunohistochemical staining showed see more expression of DEC-205 on the follicular B cells, bone marrow stroma and pulmonary airway epithelium [76]. Although found predominantly on DCs, DEC-205 is not expressed ubiquitously on all DC subsets. In the mouse thymus, all DC show DEC-205 expression, the majority of which are CD8+[77]. In contrast, murine spleen shows three subsets of DC: CD4+CD8-DEC205-CD11b+, CD4-CD8-DEC205-CD11b+ and

CD4-CD8+DEC205+CD11b-[77]. Two additional populations can be traced in the lymph nodes, which show lower expression of CD8 but high to moderate expression of DEC-205 [78]. Moreover, non-lymphoid DCs such as the Langerhans cells of the skin and also BMDCs generated in the presence of GM-CSF show high expression of DEC-205 [75,79]. While humans do not have a DC subset that is CD8+, most DCs BVD-523 order in the T cell areas of human spleen and lymph nodes co-express CD11c and DEC-205 [80,81]. In a pioneering study, Hawiger and colleagues fused an immunogenic peptide from hen egg lysozyme (HEL) to the carboxyl terminus of the heavy chain of NLDC-145 [20]. They injected mice with the hybrid antibody and found that the anti-DEC-205/HEL could deliver antigen to DCs leading to CD4+

T cell activation and proliferation. However, further investigation showed that this treatment led ultimately to the deletion of many Exoribonuclease of the antigen-specific T cells and that the remaining T cells were unresponsive and could not mount an immune response to subsequent challenge with HEL administered with complete Freund’s adjuvant (CFA), showing the induction of HEL-specific tolerance. However, when the same treatment was performed in conjunction with an agonistic anti-CD40 antibody, the outcome was prolonged T cell activation and immunity. Thus, it could be inferred that DCs in the steady state, i.e. in the absence of additional stimuli, act as inducers of antigen-specific peripheral tolerance. Subsequently, ovalbumin (OVA) was coupled chemically to anti-DEC-205 and was found to permit DCs to present a cognate peptide to OVA-specific CD8+ T cells [35]. The antibody-mediated delivery was much more efficient than administration of soluble OVA alone. In agreement with the earlier study that utilized anti-DEC-205/HEL and CD4+ T cells [20], when anti-DEC-205/OVA was targeted to DCs in the steady state in vivo there was an initial burst of proliferation of the OVA-specific CD8+ T cells which was followed by their deletion.