Practice question

MDCK, Madin-Darby Canine Kidney, line established in 1958 from kidney of healthy adult Cocker Spaniel by S.H. Madin and N.B. Darby at Naval Biological Laboratory in Berkeley. Epithelial cells from distal tubule retain characteristics including polarized growth, formation of tight junctions expressing claudin-1, occludin, and zonula occludens-1, development of high transepithelial electrical resistance exceeding 200 ohm.cm2 when cultured on permeable supports, and vectorial ion transport mediated by Na+/K+ ATPase localized basolaterally. Morphology is cobblestone epithelial-like with contact inhibition. Two major substrains exist: MDCK I forms tight high resistance monolayers >1000 ohm.cm2 suitable for barrier studies, while MDCK II exhibits lower resistance 100-200 ohm.cm2 with distinct ionic permeability and used frequently for influenza replication. Canine kidney cells express both alpha2,3 and alpha2,6 linked sialic acid receptors serving as entry receptors for avian and human influenza viruses respectively, underpinning their widespread adoption for influenza assays despite non-human origin. MDCK cultures require careful mycoplasma screening to avoid altered tight junction resistance affecting transport results. This knowledge strengthens laboratory safety, protocol reproducibility, and regulatory compliance critical for translational research and clinical applications, ensuring reliable data and workforce protection.