A 42-year old man received a living, unrelated donor kidney transplant six months ago for IgA nephropathy. An acute rejection episode within the first month resolved with corticosteroid therapy. He received valganciclovir for CMV
prophylaxis for four months. His current immunosuppression regimen is tacrolimus, mycophenolate mofetil, and prednisone. The patient feels well, but serum creatinine has risen from 1.4 mg/dL to 2.0 mg/dL during the past two weeks. He returns to your office today for follow-up.
On examination, afebrile, pulse rate is 80 per minute, and blood pressure is 146/90 mm Hg. The kidney allograft is nontender to palpation.
Serum creatinine: 2.2 mg/dL
Whole blood tacrolimus (trough) 8 ng/mL (therapeutic: 6-10)
Urinalysis: 1+ protein; 10-15 WBCs, 5-10 tubular epithelial cells/hpf
Ultrasonography shows a normal allograft and vessels; no obstruction is seen.
Biopsy reveals an interstitial lymphocytic infiltrate.
Which of the following additional tests of the biopsy specimen is most appropriate?
A. Immunostaining for IgA deposition
B. Immunostaining for polyomavirus (BK type)
C. Immunostaining for CD4 and CD8 quantitation
D. Polymerase chain reaction assay for CMV
E. In situ hybridization for TGF-β expression
(Source: Dr. Brad Denker, Beth Israel Deaconess Medical Center/Harvard Medical School)