PRF1 and immunoglobulin G4-related sclerosing disease: Recent studies show clonally expanded CD4+ cytotoxic T cells that express granzyme B, perforin, IFN-gamma, and TGF-beta1 are prominent in IgG4RD [10, 11] Rituximab-mediated B cell depletion is associated with a reduction in numbers of disease-associated CD4+ cytotoxic T cells, suggesting that B cells play an important role in the maintenance of disease-associated T cell clone [10].