Anti-Dendritic Cell Marker monoclonal antibody, clone 44E2 [PE]

Primary cicatricial alopecia (PCA) encompasses a diverse group of inflammatory diseases characterized by the irreversible replacement of hair follicle structures by fibrous tissue. Although the pathogenesis of PCA remains not fully understood, the key to its understanding might be the location of dendritic cells (DCs) inflammatory infiltrate. One of the systemic therapy of choice in PCA patients is hydroxychloroquine (HCQ). We hypothesized that DCs are implicated in PCA pathogenesis and that they might constitute the biological target of HCQ treatment. For these reasons, we investigated whether DCs could affect the antimalarial responsiveness, and if DCs might be used as predictive factor of responsiveness to HCQ. In this retrospective cohort study, 65 patients diagnosed with PCA were grouped accordingly to their response to HCQ therapy. Skin biopsies had been taken before the treatment was started. Cell count was performed on immunohistochemistry by using characteristic monoclonal antibodies to specific subpopulations of DCs. In almost every second patient (47.7%), we observed remission of the disease during HCQ treatment. The number of plasmacytoid and myeloid DCs as well as Langerhans cells in lesional skin of HCQ responders was higher in comparison with HCQ nonresponders. Moreover, in a predictive model receiver operating characteristic (ROC curve) we showed that plasmacytoid DCs might be used as a predictive factor of responsiveness to HCQ. The results of this study are important as identifying biomarkers for responsiveness to a HCQ therapy will be helpful to individualize treatment and make it more effective.

PD-L2, which has been identified as a PD-1 ligand, is specifically expressed in dendritic cells (DCs) and macrophages. The transcription factors that determine the cell type-specific expression of PD-L2 are largely unknown, although PD-1 and its ligands, which have been shown to play important roles in T cell suppression, have been vigorously analyzed in the field of cancer immunology. To reveal the mechanism by which Pdcd1lg2 gene expression is regulated, we focused on DCs, which play key roles in innate and acquired immunity. The knockdown of the hematopoietic cell-specific transcription factors PU.1 and IRF4 decreased PD-L2 expression in GM-CSF-induced mouse bone marrow-derived DCs. Chromatin immunoprecipitation assays, luciferase assays, and electrophoretic mobility shift assays demonstrated that PU.1 and IRF4 bound directly to the Pdcd1lg2 gene via an Ets-IRF composite element sequence and coordinately transactivated the Pdcd1lg2 gene. Furthermore, PU.1 knockdown reduced the histone acetylation of the Pdcd1lg2 gene. The knockdown of the typical histone acetyltransferase p300, which has been reported to interact with PU.1, decreased the expression and H3K27 acetylation of the Pdcd1lg2 gene. GM-CSF stimulation upregulated the Pdcd1lg2 gene expression, which was accompanied by an increase in PU.1 binding and histone acetylation in Flt3L-generated mouse bone marrow-derived DCs. The involvement of PU.1, IRF4, and p300 were also observed in mouse splenic DCs. Overall, these results indicate that PU.1 positively regulates Pdcd1lg2 gene expression as a transactivator and an epigenetic regulator in DCs.