Role of B cell activation through toll-like receptors in systemic lupus erythematosus 

Lupus features a wide range of symptoms and severity, making it challenging to develop effective treatments. Research has identified over 100 genetic variations (risk variants) linked to lupus, many affecting B cells (cells important in normal immune response but in lupus, they can turn against the body) and toll-like receptor (TLR) signaling. TLRs act as alarm systems that detect molecules from viruses and bacteria. In lupus, TLRs mistakenly respond to the body’s own molecules, including DNA or RNA, triggering an inappropriate immune response. While treatments targeting B cells and TLRs show promise, the diversity of lupus risk factors and symptoms remains a major hurdle.

Different TLRs affect B cells differently. Normally, TLR9 stimulation promotes regulatory B cells, which are important for controlling immune responses and preventing autoimmunity (when the immune system reacts against the body’s own cells and tissues). However, driven by the overactivation of TLR7, B cells from people with lupus do not respond correctly to this stimulation, leading to defective regulatory responses and increased Double Negative (DN) 2 B cells, the most expanded group of cells in people with active SLE.

Dr. Cervantes-DÍaz will study B cell differentiation (development or expansion) after activation by different TLR signals, using B cells and organ-like structures called tonsil-derived organoids from healthy individuals. Using advanced techniques including CRISPR (a tool that can cut and edit DNA at specific spots), he will genetically delete SLE risk genes affecting the TLR7 and TLR9 pathways to observe how these changes affect B cell development.

Dr. Cervantes-DÍaz will then compare B cell responses from healthy individuals with low and high genetic risk for lupus to those from people with SLE after TLR7 and TLR9 stimulation. He predicts that people with lupus and healthy individuals with higher genetic risk will show impaired B cell differentiation.

What this means for people with lupus
This research could lead to a better understanding of the molecular mechanisms underlying lupus and help develop more targeted and effective treatments for different people living with lupus, based on their genetic profiles.

Systemic lupus erythematosus (SLE) is a complex and chronic inflammatory disease, particularly affecting young women from minority populations. The high phenotypical heterogeneity of SLE poses a challenge for therapeutic design, emphasizing the need for deeper insights into its pathogenic mechanisms to stratify patients. With up to 60% genetic susceptibility, Genome Wide Association Studies (GWAS) have identified over 100 risk variants, mainly non-coding, associated with B cell biology and Toll-like receptor (TLR) signaling. B cell dysfunction, especially in TLR9/CpG stimulation, appears pivotal in SLE, leading to defective regulatory responses and an expansion of Double Negative (DN2) B cells. Clinical trials targeting B cells and TLRs show promise, but the heterogeneity of SLE remains a barrier. This study proposes cutting-edge technologies to characterize the differentiation trajectory of B cells activated via TLR7 and/or TLR9 in healthy subjects and SLE patients. Specific aims include characterizing B cell development stages after TLR7 and TLR9 stimulation, using both peripheral blood mononuclear cells (PBMCs) and tonsil-derived organoids. Additionally, the study aims to employ CRISPR approaches to knock out SLE risk genes affecting TLR7/TLR9 pathways. Single-cell profiling will further investigate B cell differentiation trajectories in patients and healthy individuals with varying genetic risk factors. Preliminary data showcase the applicant’s expertise in B cell characterization and organoid stimulation, offering insights into SLE risk genes and the heterogeneous subpopulations of B cells. The significance of this research lies in its innovative methodologies, utilizing genetic data, single-cell proteo-transcriptomic assays, and Germinal Center organoids to enhance understanding of SLE pathogenesis. The findings aim to correlate altered B cell states with clinical manifestations in SLE patients, preparing the way for more targeted and effective therapeutic interventions.