Indeed, the effectiveness of B cell depletion therapy in IgG4-RD suggests that B lymphocytes and other cells of this lineage play an important pathological role, probably via their interaction with CD4+ cytotoxic T lymphocytes (CTL) serving as effective antigen-presenting cells and/or through the secretion of B cell-derived growth factors [42, 43]. The gene discussed is CD4; the disease is immunoglobulin G4-related sclerosing disease.