Plasmablasts: A promising biomarker in IgG4-related disease

Abstract

Plasmablasts appear to play a central role in the pathophysiology of IgG4-related disease (IgG4-RD). These cells are CD19lowCD20-CD27+CD38bright on flow cytometry and their absolute numbers in patients with IgG4-RD are dramatically higher in those patients than in healthy controls. Plasmablasts likely contribute to the pathogenesis of IgG4-RD through a variety of ways: (1) autoantibody production; (2) myofibroblast activation; (3) profibrotic cytokine production; or, (4) antigen-presentation to putative pathogenic T cells. This chapter introduces the reader to the concept of plasmablasts, reviewing the origin and biology of these cells, the processes of somatic hypermutation, affinity maturation, and class-switch recombination. It also discusses the identification of plasmablasts by flow cytometry and reviews the evidence for these cells’ centrality in the B cell-T cell crosstalk that is crucial to IgG4-RD.