Atypical Presence of Antimyeloperoxidase Antibodies in 2 Transplanted Patients

Dear Sir, Transplanted kidneys can develop different types of vascular lesions which can be due to cyclosporin A (CyA) toxicity [1, 2] or to rejection manifestations [4]. We evaluated the sera of 54 transplanted patients for ANCA (antineutrophil cytoplasm antibodies). ANCA were tested with immunofluorescence (for cytoplasmic or perinuclear fluorescence pattern) and ELISA (Biocarb Diagnostics ‘Anti-Neutrophil Cytoplasmic Quantitative Kit’, Lund, Sweden). This kit detects antiproteinase 3 antibodies (PR3-Abs). Moreover ELISA was performed for antimyeloperoxidase antibodies (MPO-Abs, Biocarb Diagnostics ‘Anti-Myeloperox-idase Quantitative Kit’, Lund, Sweden). All the patients were negative for PR3-Abs. All the patients but 2 (patient 1 and 2) were negative for MPO-Abs. Patient 1 was transplanted in 1989 with a cadaveric kidney. His causal nephropathy was a type II (granular fluorescence) extracapillary proliferative glomerulonephritis (GN) (biopsy of 1986), without signs of necrosis or of vascular involvement, which led to end stage renal disease in 1986. His sera were collected during the dialysis period and after the transplantation. Sera of the previous period were lacking. A transplant biopsy performed in July 1989 showed signs of CyA acute toxicity. From the clinical point of view this patient has a stable renal function (serum creatinine 1.8 mg% since August 1989), absent proteinuria, no clinical or laboratory signs of vasculitis. Lymphocytotoxic activity against a selected panel was 30%. Patient 2 was biopsied in 1970 for a ne-phrotic syndrome: membranoproliferative GN (MPGN) was detected. Hemodialysis was begun in 1978 and the patient received a cadaveric kidney in 1984. She had an acute rejection episode (on the 1st day) which was successfully treated. Her serum creatinine was stable (1.2-1.4 mg%) and proteinuria ranged from 0.1 to 0.4 g/day. This patient had no antiHLA antibodies. Sera of this patient were collected since 1984; the most recent ones were clearly positive for MPO-Abs; the older sera showed borderline values.