Cellular and molecular determinants mediating the dysregulated Germinal Center immune dynamics in Systemic Lupus Erythematosus. Authors

Spiros Georgakis ^1* Kalliopi Ioannidou ¹ Bernat Bramon Mora ² Michail Orfanakis ¹ Cloe Brenna ¹ Yannick Daniel Muller ³ Perla M Del Rio Estrada ^4,5 Ashish Arunkumar Sharma ⁴ Giuseppe Pantaleo ³ Laurence de Leval ¹ Denis Comte ² Raphael Gottardo ² Constantinos Petrovas ^1*

• ¹ Department of Laboratory Medicine and Pathology, Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Switzerland
• ² Centre Hospitalier Universitaire Vaudois (CHUV), Lausanne, Vaud, Switzerland
• ³ Division of Immunology and Allergy, Lausanne University Hospital, Lausanne, Geneva, Switzerland
• ⁴ Emory University, Atlanta, Georgia, United States
• ⁵ Departamento de Investigación en Enfermedades Infecciosas (CIENI), Mexico, Mexico

Systemic lupus erythematosus (SLE) is characterized by dysregulated humoral immunity, leading to the generation of autoreactive B cells that can differentiate both within and outside of lymph node (LN) follicles. Here, we employed spatial transcriptomics and multiplex imaging to investigate the follicular immune landscaping and the in situ transcriptomic profile in LNs from SLE individuals. Our spatial transcriptomic analysis revealed robust type I IFN and plasma cell signatures in SLE compared to reactive, control follicles. Cell deconvolution revealed that follicular T cell subsets are mainly affected by the type I IFN fingerprint of SLE follicles. Dysregulation of TFH differentiation was documented by i) the significant reduction of Bcl6 hi TFH cells, ii) the reduced cell density of potential IL-4 producing TFH cell subsets associated with the impaired transcriptomic signature of follicular IL-4 signaling and iii) the loss of their correlation with GC-B cells. This profile was accompanied by a marked reduction of Bcl6 hi B cells and an enrichment of extrafollicular CD19 hi CD11c hi Tbet hi , ageassociated B cells (ABCs), known for their autoreactive potential. The increased prevalence of follicular IL-21 hi cells further reveals a hyperactive microenvironment in SLE compared to control. Taken together, our findings highlight the altered immunological landscape of SLE follicles, likely fueled by potent inflammatory signals such as sustained type I IFN and/or IL-21 signaling. Our work provides novel insights into the spatial molecular and cellular signatures of SLE follicular B and TFH cell dynamics, and points to druggable targets to restore immune tolerance and enhance vaccine responses in SLE patients.