A. BK virus particles from the urine (× 180,000). B. BK virus particles (V) in nuclei (N) of epithelial cells lining the lumen (L) of the donor ureter. (× 6000). (Inset: virus particles in outlines area, × 22,500.) From (24) Gardner S, Field A, Coleman D, Hulme B. New human papovavirus (B.K.) isolated from urine after renal transplantation. Lancet 1971; 297: 1253-1257, reprinted with permission from Elsevier.