bioRxiv2024
BackgroundChemokines play critical roles in the recruitment and activation of immune cells in both homeostatic and pathologic conditions. Here, we examined chemokine ligand-receptor pairs to better understand the immunopathogenesis of cutaneous lupus erythematosus (CLE), a complex autoimmune connective tissue disorder. ObjectivesOur objectives were to (1) characterize the cellular and proteomic constitution of interface dermatitis in CLE using blister biopsies, (2) map chemokine:ligand receptor pairs that govern recruitment of immune cells to form interface dermatitis in CLE, and (3) perform unbiased analyses in tandem on different clinical subtypes to identify novel genes and proteins underlying discoid versus subacute CLE. MethodsWe used suction blister biopsies to measure cellular infiltrates with spectral flow cytometry in the interface dermatitis reaction, as well as 184 protein analytes in interstitial skin fluid using 96-plex immunoassay targeted proteomics. Flow and 96-plex immunoassay data concordantly demonstrated significant increases in T cells and antigen presenting cells (APCs). We also performed spatial transcriptomics and spatial proteomics of punch biopsies using digital spatial profiling (DSP) technology on CLE skin and healthy margin controls to examine discreet locations within the tissue. ResultsSpatial and 96-plex immunoassay data confirmed elevation of interferon (IFN) and IFN-inducible CXCR3 chemokine ligands. Comparing involved versus uninvolved keratinocytes in CLE samples revealed upregulation of essential inflammatory response genes in areas near interface dermatitis, including AIM2. 96-plex immunoassay data confirmed upregulation of Caspase 8, IL-18 which is the final product of AIM2 activation, and induced chemokines including CCL8 and CXCL6 in CLE lesional samples. Chemotaxis assays using PBMCs from healthy and CLE donors revealed that T cells are equally poised to respond to CXCR3 ligands, whereas CD14+CD16+ APC populations are more sensitive to CXCL6 via CXCR1 and CD14+ are more sensitive to CCL8 via CCR2. ConclusionsTaken together, our data map a pathway from keratinocyte injury to lymphocyte recruitment in CLE via AIM2-Casp8-IL-18-CXCL6/CXCR1 and CCL8/CCR2, and IFNG/IFNL1-CXCL9/CXCL11-CXCR3, and identify potential novel biomarkers of disease. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=168 SRC="FIGDIR/small/574422v2_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@1e86dbeorg.highwire.dtl.DTLVardef@7d0208org.highwire.dtl.DTLVardef@1108aa8org.highwire.dtl.DTLVardef@ff255f_HPS_FORMAT_FIGEXP M_FIG C_FIG Model of chemokine systems governing recruitment of immune cell subsets to form interface dermatitis in cutaneous lupus. A. Summary of fresh tissue blister biopsy studies demonstrating increases in HLADR+ cells in nonlesional lupus biopsies as assessed by flow cytometry, and increased CXCL6 and CCL8 as assessed by 96 plex immunoassay. Lesional lupus biopsies also demonstrated significant increases in T cells and CXCL9/10/11 production. B. Model of chemokine-directed formation of interface dermatitis in cutaneous lupus. 1. Whole transcriptome atlas (WTA) digital spatial profiling (DSP) revealed increased AIM2 in keratinocytes proximal to inflammation, which is reported to be induced by environmental triggers including UV light and toxins. We also noted increased Caspase 8 (Casp8) and IL18 at the protein level, which can be induced downstream of AIM2. Chemokines including CXCL6 and CCL8 can be induced downstream of IL18, explaining how CCL8 and CXCL6 might be induced. 2. Recruitment of myeloid cell first responders by CCL8 and CXCL6. CD14+CD16+ myeloid cells, which were recently described in nonlesional lupus skin, express CXCR1 and migrate towards CXCL6, whereas CD14+CD16-myeloid cells express more CCR2 and migrate towards CCL8. 3. The CXCR3 ligands CXCL9/10/11 are expressed by keratinocytes, but more strongly in CD45+ immune cell and T cell regions of interest (ROIs). 4. T cells express CXCR3 and migrate towards CXCL9 and to a greater extent CXCL11. 5. The recruited HLADR+ myeloid populations and T cells contribute to formation of interface dermatitis. Thus, we propose a model in which keratinocyte/myeloid crosstalk can reinforce chemokine systems to optimally recruit lymphocytes and other immune cells to form interface dermatitis. Created with Biorender.com. Plain language summaryLupus skin rashes arise during flares, after exposure to medications or sunlight, or in response to other triggers of inflammation. To understand how white blood cells enter the skin to cause these rashes, we used new technologies to look at proteins that attract them into the skin. We found proteins that are expressed by skin cells in lesions that can recruit specific types of white blood cells that are thought to be the initiators of skin rashes. Once in the skin, these and other white blood cells can make additional proteins that bring in more and more cells. We hope that our findings will be used to test new topical treatments for lupus and other autoimmune skin rashes.