De novo oligoclonal expansions of circulating plasmablasts in active and relapsing IgG4-related disease

Clonally expanded CD19+CD27+CD20−CD38hi plasmablasts are a hallmark of active IgG4-RD. Enhanced somatic mutation in activated B cells and plasmablasts and emergence of distinct plasmablast clones on relapse indicate that the disease pathogenesis is linked to de novo recruitment of naive B cells into T cell-dependent responses by CD4+ T cells, likely driving a self-reactive disease process.