Background: Immune tolerance prevents the immune system to recognise and react against self-antigens. These mechanisms are highly regulated by dendritic cells through their interaction with T cells. In the pathogenesis of Systemic Lupus Erythematosus (SLE), the loss of self-tolerance plays a key role, with environmental and genetic factors contributing to its development. Tolerogenic dendritic cells (tolDCs) represent a potential resource to restore tolerance in autoimmune diseases due to their capability to induce anti-inflammatory and regulatory immune responses. Allele-specific expression (ASE) can be used to identify gene regulatory mechanisms relevant to cellular phenotype and mechanisms, especially in complex diseases.

Objectives: This study aims to characterize the ASE during tolerance induction on dendritic cells (DCs) from Mexican women with SLE.

Methods: Volunteers were identified through the LupusRGMX. Blood and buccal swabs were collected. From blood, monocytes were isolated using Lymphoprep and a magnetic beads cell-enrichment kit. For each volunteer, two wells were seeded and cultured in RPMI-1640 medium: monocyte-derived dendritic cells (moDCs) were supplemented with GM-CSF and IL-4 every 48 hours, whereas tolDCs were supplemented with GM-CSF and IL-4 every 48 hours and IL-10 daily. On the 7th day, cells were separated into two wells and supplemented as previously described, one well per condition was additionally supplemented with imiquimod (IMQ) (Figure 1). Flow cytometry analysis, RNAseq, differential gene expression, whole genome sequencing, variant discovery and allele-specific expression analyses were performed.

Results: Samples were obtained from 23 women with SLE and 10 controls. Flow cytometry was performed to analyze surface markers associated with DCs differentiation and function; a higher percentage of cells positive for CD11c and CD14 was observed in cells after the differentiation in SLE and healthy controls. No differences were observed in the expression of CD40 and HLA between cell types in healthy controls, whereas CD80 was more expressed in cells after differentiation. This pattern was equally observed in volunteers with SLE with non-significant differences, still higher variability was observed in participants with non-corticosteroid treatment. Upon comparison of RNA-seq data between different cell types from volunteers with SLE we noted an upregulation of genes previously proposed as markers for SLE. For instance, when comparing monocytes with moDCs we observed upregulated expression of APOE, which has been reported to be elevated in patients with active SLE. CCL13 expression was upregulated in both moDCs and tolDCs when compared with monocytes; chemokines play a crucial role in recruiting inflammatory cells, specifically CCL13 has been previously reported in tissue lesions on other autoimmune diseases such as rheumatoid arthritis. These genes were also upregulated on moDCs and tolDCs from healthy volunteers. For both moDCs and tolDCs we observed an important enrichment of genes associated with the response to stimulus. When comparing monocytes from healthy individuals and SLE volunteers, we observed an upregulation of genes associated with defense response and interferon-mediated signaling pathways, genes and processes previously proposed as markers for SLE, such as IFI44 and SIGLEC1. For moDCs we saw an enrichment of genes associated with DNA repair and apoptosis clearance, both processes relevant in autoimmune diseases. In tolDCs we observed an important enrichment of genes contributing to lipid metabolisms, such as ABCG1; dysregulation of lipid metabolism could be leading to DCs dysfunction and loss of tolerance in SLE.

Conclusion: Further integration of the genomic and transcriptomic data will allow us to deepen the regulatory mechanisms involved in the tolerance induction on DCs. The understanding of these mechanisms could contribute to the design and development of new specific and personalized approaches to the diagnosis and treatment of SLE.

REFERENCES: NIL.

Acknowledgements: This work received support from Luis Aguilar, and Jair García of the Laboratorio Nacional de Visualización Científica Avanzada. We also thank Carina Uribe Díaz, and Alejandra Castillo Carbajal for their technical support.

Disclosure of Interests: Ana Laura Hernández-Ledesma: None declared, Sofía Salazar-Magaña: None declared, Evelia Lorena Coss-Navarrete: None declared, Karen Julia Nuñez-Reza: None declared, Lizbet Tinajero Nieto: None declared, Angélica Peña-Ayala: None declared, Estefania Torres-Valdez: None declared, Guillermo Felix Rodríguez: None declared, Gabriel Frontana-Vázquez: None declared, Florencia Rosetti: None declared, Selene L Fernández-Valverde: None declared, Maria Gutierrez Arcelus: None declared, Deshire Alpizar-Rodriguez GSK Mexico. Unrelated to this abstract., Alejandra Medina-Rivera: None declared.