PLA2R1 and idiopathic membranous glomerulonephritis: Third, almost all patients with MGN in the setting of IgG4-RD are negative for circulating anti-M type phospholipase A2 receptor (PLA2R) antibody by serology and for PLA2R staining in renal tissue, whereas PLA2R is the most common target antigen in primary MGN [70, 75].