IgG4-related disease (IgG4-RD) is a fibroinflammatory disorder in which IgG4+ B cells and T cells interact to drive chronic organ inflammation. Patients with multiorgan involvement may become refractory to standard therapy, resulting in progressive organ damage and risk of organ failure. Here, we report a patient with treatment-refractory multiorgan IgG4-RD treated with CD19-directed chimeric antigen receptor (CAR) T cells and describe the clinical and immunologic effects over more than 12 months of follow-up. A 60-year-old man with IgG4-RD involving the pancreas, hepatobiliary tract, and lungs, who was refractory to long-term immunosuppression, received autologous CD19-directed CAR T cells. Disease course was monitored longitudinally and multimodal immune profiling was performed on peripheral blood. CAR T cell therapy was well tolerated, with only grade 1 cytokine release syndrome, no neurotoxicity, and transient cytopenias without infections. Treatment induced B-cell aplasia lasting 6 months, while serum IgG4 levels normalized by month 8 and remained within the reference range thereafter. FAPI (fibroblast activation protein inhibitor) PET/CT demonstrated regression of fibroinflammatory activity, accompanied by improved lung function and quality of life. Immunosuppressive therapy was completely discontinued without disease flares for more than 12 months. B cell reconstitution consisted predominantly of naïve and transitional subsets. This was paralleled by a decline in T follicular helper cells and CD4+ cytotoxic T cells and attenuation of fibro-inflammatory and B cell-mediated signaling networks on interactome analyses. In this treatment-refractory case of multiorgan IgG4-RD, CD19-directed CAR T cell therapy induced durable, treatment-free remission with normalization of serum IgG4 and improvement across multiple clinical endpoints. Multimodal immune profiling indicates that CAR T cells can reset the B cell compartment and dampen pathogenic T cell and stromal interactions, supporting prospective evaluation of CAR T cell therapy in IgG4-RD.

Immunoglobulin G4-related sclerosing cholangitis (IgG4-SC), also termed IgG4-related cholangitis (IRC), is a challenging immune-mediated biliary disease, frequently mimicking malignancies such as cholangiocarcinoma (CCA) or other sclerosing cholangitides like primary sclerosing cholangitis (PSC). Accurate diagnosis is critical to avoid unnecessary surgical interventions. This mini-review aims to synthesize the most current evidence on the pathogenesis, diagnostic pitfalls, and management strategies for IgG4-SC, with a focused discussion on overcoming diagnostic dilemmas and addressing the significant challenge of disease relapse. The pathogenesis of IgG4-SC involves a complex interplay of genetic predisposition, environmental triggers (e.g., industrial vapors, dust, gases, fumes, and asbestos), and dysregulated adaptive immunity. A distinctive CD4+ T-cell response, dominated by T-helper 2 (Th2), follicular helper T (Tfh) cells, and regulatory T cells (Tregs), drives B-cell activation, oligoclonal expansion of IgG4+ plasmablasts, and progressive fibrosis. Notably, the discovery of IgG4/IgG1 autoantibodies against annexin A11 and laminin 511-E8 has provided insight into potential direct pathogenic mechanisms. Diagnosis relies on a multimodal approach integrating clinical presentation, characteristic imaging findings, elevated serum IgG4 levels (with levels >2× ULN being suggestive, and >4× ULN being highly specific), the IgG4/IgG1 ratio (>0.24), other organ involvement (notably type 1 autoimmune pancreatitis, AIP), supportive histopathology, and a rapid response to corticosteroid therapy. Despite high initial response rates to steroids, relapse occurs in 30%-50% of patients. Maintenance therapy with steroid-sparing immunomodulators (e.g., azathioprine, mycophenolate mofetil) or B-cell depleting agents such as rituximab is often required. The anti-CD19 monoclonal antibody inebilizumab has emerged as a potent new option for maintaining remission. Maintaining a high index of clinical suspicion for IgG4-SC is essential in patients with obstructive jaundice and biliary strictures. Future efforts should focus on validating specific biomarkers (e.g., circulating plasmablasts, autoantibody profiles) and developing evidence-based protocols for long-term management to prevent fibrotic complications and reduce the relapse rate.

IgG4-related cholangitis (IRC) is the major hepatobiliary manifestation of IgG4-related disease (IgG4-RD), a systemic fibroinflammatory disorder. The pathogenesis of IgG4-RD and IRC is currently viewed as multifactorial, as there is evidence of a genetic predisposition while environmental factors, such as blue-collar work, are major risk factors. Various autoantigens have been described in IgG4-RD, including annexin A11 and laminin 511-E8, proteins which may exert a partially protective function in cholangiocytes by enhancing secretion and barrier function, respectively. For the other recently described autoantigens, galectin-3 and prohibitin 1, a distinct role in cholangiocytes appears less apparent. In relation to these autoantigens, oligoclonal expansions of IgG4+ plasmablasts are present in patients with IRC and disappear upon successful treatment. More recently, specific T-cell subtypes including regulatory T cells, follicular T helper 2 cells, peripheral T helper cells and cytotoxic CD8+ and CD4+ SLAMF7+ T cells have been implicated in the pathogenesis of IgG4-RD. The clinical presentation of IRC often mimics other biliary diseases such as primary sclerosing cholangitis or cholangiocarcinoma, which may lead to inappropriate medical and potentially invalidating surgical interventions. As specific biomarkers are lacking, diagnosis is made according to the HISORt criteria comprising histopathology, imaging, serology, other organ manifestations and response to therapy. Treatment of IRC aims to prevent or alleviate organ damage and to improve symptoms and consists of (i) remission induction, (ii) remission maintenance and (iii) long-term management. Glucocorticosteroids are highly effective for remission induction, after which immunomodulators can be introduced for maintenance of remission as glucocorticosteroid-sparing alternatives. Increased insight into the pathogenesis of IRC will lead to improved diagnosis and novel therapeutic strategies in the future.

Follicular cholecystitis (FC) is a poorly characterized entity. To determine its frequency/clinicopathologic associations. A total of 2550 cholecystectomy specimens were examined. Two hundred three of these were consecutive routine cholecystectomies submitted entirely for microscopic examination to determine the relative frequency of incidental pathologies in gallbladders (GBs). The remainder had representative sampling. Underlying conditions were nonobstructive pathologies (1270 nonspecific cholecystitis), obstructive (62 distal biliary tract tumors, 35 primary sclerosing cholangitis, and 31 autoimmune pancreatitis), and neoplastic (n = 949). FC was defined as 3 distinct lymphoid follicles (LFs)/centimeter. In the GBs totally submitted for microscopic examination, the true frequency of FC was found to be 2.5% (5/203), and in the representatively sampled group, it was 1.9%, with similar frequencies in nonobstructive, obstructive, and neoplastic cases (2.3%, 3.1%, and 1.3%, respectively, P = .77). When the 39 FC in nonneoplastic GBs contrasted with ordinary chronic cholecystitis, they were associated with older age (68 vs 49 years, P < .0001), similar gallstone frequency (68 vs 81%), female/male ratio (2.7 vs 2.6), and wall thickness (4 mm for both). None had lymphoma/parasites/Salmonella infection. Of 17 cases who had undergone gastric biopsy, 5 had chronic gastritis (2 with Helicobacter pylori). Microscopically, the LFs were the main inflammatory process often with minimal intervening inflammation. IgG4-positive plasma cell density was low (<10/high-power field) in 21/24(87.5%) cases. Follicular cholecystitis is seen in 2% of cholecystectomies, typically in significantly older patients, suggesting a deranged immune response. A third of the patients reveal biopsy-proven gastritis. FC does not seem to be associated with autoimmunity, lymphoma, or obstructive pathologies.