HLA-DQB2 is specifically expressed in LCH CD1c⁺mDCs, CD1a⁺CD207⁻, CD1a⁺CD207^low, and CD1a⁺CD207^highsubpopulations. (A) Scatter plots illustrate expression of 6 genes (CD1a, CD1c, CD207, TNFα, HLADQA2, and HLADQB2) among the top 50 most overexpressed genes in LCH CD1a⁺CD207⁺ DCs relative to healthy donor blood CD1c⁺ mDCs. Gene-expression profiles were obtained from FACS-sorted LCH lesion CD1a⁺CD207⁺ DCs (n = 11) and blood CD1c⁺ mDCs (n = 3) from healthy donors. Affymetrix Human Transcriptome Array 2.0 Platform was used for this study. All samples used in the study are listed in supplemental Table 3a. (B) Control skin specimens (n = 4), peripheral blood samples (n = 4) from healthy donors, and lesion from LCH patients (n = 6) were FACS-purified. RNA was extracted, cDNA was amplified and then the HLA-DQB2 expression was determined by qPCR (normalized to GAPDH messenger RNA [mRNA] expression). HLA-DQB2 expression was detected in lesion CD1a⁺ populations as well as CD1c⁺ mDCs, but not in other lineages, consistent with BRAFV600E distribution. Epidermal LCs were used as a positive control. Technical duplicates were used. LCH samples used in the study are listed in supplemental Table 3b. (C) Overlay histograms of HLA-DQB2 surface expression in 6 LCH lesion subpopulations (colored) compared with control (gray) demonstrates increasing surface expression of HLA-DQB2 from lesion CD1c⁺ mDCs through CD1a⁺CD207⁺ populations.