Tissue Distribution of the DEC-205 Protein That Is Detected by the Monoclonal Antibody NLDC-145: I. Expression on Dendritic Cells and Other Subsets of Mouse Leukocytes

Prior studies by a variety of groups demonstrated that the mAb NLDC-145 reacted primarily with dendritic cells (DCs) and the epithelial cells of the thymic cortex. We recently reported that this mAb recognizes DEC-205, a 205-kDa integral membrane glycoprotein with a unique amino-terminal sequence, and raised a rabbit polyclonal antibody to purified DEC-205 with higher affinity for the blotted antigen than the original mAb. Here we utilize both the polyclonal and NLDC145 to reassess the expression and function of DEC-205 on leukocytes. By cytofluorography, DCs derived from the epidermis (Langerhans cells) and from proliferating bone marrow progenitors (BMDCs) expressed high levels (2-3 logs) of DEC-205, while freshly isolated spleen DCs comprised two subsets, most (80%) staining at low levels (< log), the remainder moderately (1.5 logs). DEC-205 epitopes were sensitive to trypsin, but were regenerated in culture. Resident and inflammatory peritoneal macrophages did not express the antigen, except for small amounts on thioglycollate-elicited cells. B cells from spleen, lymph node, bone marrow, blood, and peritoneal fluid expressed levels of DEC-205 that were 10- to 50-fold lower than those on BMDCs. Marrow pro- and pre-B cells did not express DEC-205. Polyclonal anti-DEC-205 failed to inhibit either stimulation of a primary mixed leukocyte reaction by DCs in vitro, or a local graft vs host response in vivo, where parental T cells were injected into F1 mice. DEC-205 is therefore more broadly expressed on leukocytes than previously appreciated, but its function remains unclear.