Figure 6. Antibody against the M-Type Phospholipase A₂ Receptor (PLA₂R) and Disease Activity in a Patient with Membranous Nephropathy.

Serum samples were collected serially from a patient with membranous nephropathy who had clinical remission after receiving immunosuppressive treatment with cyclophosphamide and prednisone (see the Clinical Vignettes section in the Supplementary Appendix). Panel A shows a decline in the urinary protein level (as measured by the protein-to-creatinine ratio) and an increase in the serum albumin level. The results of Western blotting of serum samples taken from the patient at the same times as the laboratory measurements (Panel B) show reactivity to PLA₂R, either the 185-kD native form not deglycosylated by peptide N-glycosidase F (PNGase F−) or the 145-kD deglycosylated form (PNGase F+) in the initial serum sample (from December 2005) only. Equal loading is verified by the nonspecific detection of a 98-kD band. Equal volumes of the four serial serum samples were electrophoresed and blotted with anti–human IgG antibody (bottom), with a progressive increase in total IgG after the patient entered a period of remission from membranous nephropathy.