Examination of the Level of Circulating Plasmablasts and Their Characteristics as Diagnostic Tools for Immunoglobulin G4-related Disease.

Background: Immunoglobulin G4-related disease (IgG4-RD) is a chronic, immune-mediated condition characterized by fibro-inflammatory lesions with lymphoplasmacytic infiltration. Diagnosis traditionally relies on histopathological findings, including the presence of IgG4+ plasma cells. However, due to challenges in biopsy accessibility, additional measures are needed to facilitate diagnosis.

Objectives: To identify additional parameters for characterizing IgG4-RD patients.

Methods: We compared several circulating factors between a cohort of patients with IgG4-RD disease seen at our hospital between 2017 and 2023 and healthy controls.

Results: Among 16 suspected patients, 13 were confirmed to have IgG4-RD, and 3 were classified as highly likely. Comparison with controls revealed differences in white blood cell count (WBC) (Folf change (FC) 1.46, P < 0.05), plasmablasts (FC 3.76, P< 0.05), plasmablasts CD38 (FC 1.43, P < 0.05), and CD27 (FC 0.66, P = 0.054), thus highlighting potential markers for IgG4-RD diagnosis. Treatments with steroids/rituximab tend to reduce plasmablast (FC 0.6) and IgG4 (FC 0.28) levels and to increase Gal-3 levels.

Conclusions: Levels of plasmablasts are a significant diagnostic feature in IgG4-RD. Healthy individuals have a lower level of plasmablasts. Elevated Gal-3 in serum of patients with IgG4-RD suggests a role in plasmablast activation. CD38/CD27 expression by plasmablasts emerges as a potential marker. Further research on a larger cohort is needed to confirm these findings.