RK13 is an immortalized epithelial cell line that was established from the kidney tissue of a 5-week-old rabbit (Oryctolagus cuniculus). The line is often employed in transfection experiments and to isolate viruses. Testing indicates that RK13 cells can support the growth of rabbitpox, herpes simplex, pseudorabies virus, myxoma, B virus, vaccinia, simian adenoviruses, and rubellavirus. In the 1990s, it was discovered that the RK13 line and many other cell lines were contaminated the bovine viral diarrhea virus (BVDV). Though the virus was subsequently eliminated from some of the lines, the RK13 rabbit kidney cell line continues to test positive for BVDV.

Similar to other epithelial cells, RK13 cells stain positive for the protein keratin. In most epithelial cells, the keratin cytoskeleton extends throughout the cytoplasm from the surface of the nucleus to the periphery of the cell. At the periphery, the keratin cytoskeleton interacts with desmosomes and hemidesmosomes. Extremely stable, filaments of keratin provide significant structural strength to epithelial cells and the sheets they naturally have a tendency to form.

The rabbit kidney epithelial (RK13) cell culture illustrated above was transfected with a recombinant plasmid vector containing a chimeric fusion gene product of DsRed fluorescent protein. In addition, the cells were treated with the popular nuclear counterstain Hoechst 33342. Images were recorded in grayscale with a 12-bit digital camera coupled to a Nikon Eclipse 80i microscope equipped with bandpass emission fluorescence filter optical blocks. During the processing stage, individual image channels were pseudocolored with RGB values corresponding to each of the fluorophore emission spectral profiles.