Plasmablast Storms: Microbial Drivers of Acute and Chronic Autoimmune Flares.

Autoimmune flares are often accompanied by abrupt surges of circulating plasmablasts-short-lived, high-output antibody-secreting cells generated through extrafollicular B-cell activation in response to microbial cues. Three categories of microbial input appear to repeatedly trigger these "plasmablast storms": latent herpesvirus reactivations (Epstein-Barr virus, cytomegalovirus, human herpesvirus-6, varicella-zoster virus), acute respiratory or gastrointestinal infections including SARS-CoV-2, and chronic oral or gut dysbiosis. Although biologically distinct, these stimuli converge on innate sensing pathways driven by pathogen-associated molecular patterns such as unmethylated CpG DNA, single-stranded RNA, lipopolysaccharide, and bacterial lipoglycans. Through Toll-like receptors and type I interferon signalling, microbial signatures accelerate class switching, amplify inflammatory cytokine milieus, and lower B-cell activation thresholds, enabling rapid plasmablast mobilisation. Dysbiosis further maintains B cells in a hyper-responsive state by disrupting mucosal homeostasis and altering microbial metabolite profiles, thereby reducing the stimulus required to trigger plasmablast bursts. Once generated, these waves of oligoclonal plasmablasts home to inflamed tissues, where chemokine and adhesion landscapes shape their retention during flares. Emerging evidence suggests that such episodic plasmablast expansions promote autoantibody diversification, somatic hypermutation, and epitope spreading, progressively eroding tolerance. This review synthesizes these insights into a unified model in which infections and dysbiosis promote microbe-licensed plasmablast storms that influence the tempo and severity of autoimmune disease.