066 Plasmacytoid dendritic cells are not major producers of type 1 interferons in cutaneous lupus

Type 1 interferons (IFN-1) are major drivers of disease activity in systemic (SLE) and cutaneous lupus erythematosus (CLE). Plasmacytoid dendritic cells (pDCs) the producers IFN-1 during viral infection. pDCs reduced circulation SLE have recently been shown to an exhausted phenotype, suggesting that pathogenic were located end organs. We performed imaging mass cytometry treatment naïve CLE skin (n=48), which revealed only 8.5% (IQR 0.0-22.22) IFNa+. Across all biopsies, second lowest contributor absolute IFNa+ (Median 1; IQR 0-4.5), with B lymphocytes being smallest contributor. Classic (cDCs) macrophages (Mf) largest relative contributors IFNa CLE. For IFNb, 16.7% positive, compared 60.7% CD14+CD16+ Mf. also IFNb+ 0-7), again lowest. then mRNA situ hybridization for CLEC4C (BDCA2) (a, b, k) genes confirm these findings. was detected ITGAX (CD11c) positive cDCs but we did not identify colocalization mRNA. eluted leukocytes from flow cytometry. Flow showed a median 5.2% 3.8-9.6), other myeloid cell lineages such as CD68+ Mf 35.9% (26.4-40.7), M1 23.7% (21.6-31.7), M2 (26.4-40.7). CyTOF on PBMCs 41-marker panel, including pan-IFNa demonstrated minimal staining lineages. Taken together, findings suggest may play central role larger numbers percent. through IFN-1-independent mechanisms.