Circulating antibodies against thrombospondin type-i domain-containing 7A in chinese patients with idiopathic membranous nephropathy

Abstract

Background and objectives Thrombospondin type-I domain–containing 7A (THSD7A) was recently identified as the target antigen in about 10% of patients with M-type phospholipase A2 receptor (PLA2R)–negative membranous nephropathy in European and North American populations. The prevalence of THSD7A in other populations and their clinical associations deserve further clarification. Design, setting, participants, & measurements Immunofluorescence assay was performed to investigate anti-THSD7A antibodies in 578 consecutive patients with biopsy-proven idiopathic membranous nephropathy, 114 patients with secondary membranous nephropathy, 64 disease controls, and 20 healthy controls. Glomerular expression of THSD7A antigen was examined by immunohistochemistry. Anti-PLA2R antibodies and glomerular PLA2R expression were also screened. Results Among the 578 patients with idiopathic membranous nephropathy, 12 (2%) patients were identified as THSD7A-positive: ten patients were THSD7A-positive alone, which accounted for 16% (ten of 64) of PLA2R-negative patients; two patients were dual-positive for both anti-THSD7A and anti-PLA2R antibodies and showed enhanced expression of both antigens colocalized in glomeruli. Among the 114 patients with secondary membranous nephropathy, one among 44 (2%) patients with cancer had anti-THSD7A antibodies, whereas 18 of 44 (41%) had anti-PLA2R antibodies. No anti-THSD7A antibody was detected in other disease controls or healthy individuals. Clinical features were comparable between the patients with and without THSD7A. During follow-up, two patients who achieved remission had a clearance of circulating antibodies against THSD7A, whereas antibodies increased in parallel with proteinuria in a patient with a relapse. Conclusions THSD7A-associated membranous nephropathy has a low prevalence in Chinese patients. The double-positive patients suggest dual autoimmune responses.