Background/Purpose: The transcription factor Interferon Regulatory Factor 5 (IRF5) plays a crucial role in the functioning of several cell types such as macrophages, dendritic, and B cells. In Systemic Lupus Erythematosus (SLE), the IRF5 gene locus has been identified as a risk factor with various single nucleotide polymorphisms (SNPs) that demonstrate a strong correlation with disease development. It has been demonstrated that these polymorphisms cause increased production of IRF5 protein. In this study we investigate the effects of IRF5 overexpression in B cells on apoptosis. We hypothesized that overexpression of IRF5 would decrease activation-induced apoptosis. This would reduce tolerance and likely contribute to the development of lupus or other autoimmune diseases.

Methods: A lentivirus transduction system was engineered by cloning the human IRF5 gene into the bicistronic lentivirus pUltra-Chili, which expresses the reporter dTomato along with IRF5. Naïve B cells were isolated from healthy donors and transduced with our lentivirus construct with and without IRF5. The cells were then stimulated with IgG anti-Igm to induce activation. As an added control, a population of un-transduced naïve B cells was also stimulated. Forty-two hours post stimulation, apoptosis was measured by Annexin V staining and flow cytometry, with naïve B cell populations being gated on dTomato expression. Statistical analysis was done using the Wilcoxon signed-rank and p values with an alpha less than 0.05 were considered significant.

Results: Anti-IgM treated naïve B cells showed increased apoptosis compared to non-stimulated samples as expected. Comparing naïve B cells overexpressing IRF5 with naïve B cells treated with the empty vector, the IRF5 overexpressing cells demonstrated, on average, 46.5 % less apoptosis (p < 0.05).

Conclusion: These results support our hypothesis that overexpression of IRF5, which is a result of lupus-associated IRF5 SNPs, decreases apoptosis in activated B cells after B cell receptor engagement. This could provide a greater risk of breaking self-tolerance in individuals with the IRF5 risk haplotype.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/decreased-b-cell-activation-induced-apoptosis-in-cells-overexpressing-interferon-regulatory-factor-5-irf5-a-gene-associated-with-risk-for-systemic-lupus-erythematosus-and-other-autoimmune-diseases/