The LLC-MK2 line was initiated from a pooled cell suspension prepared from kidneys removed from six adult rhesus monkeys (Macaca mulatta) in the mid-1950s. The cell line is often utilized as a host in transfection experiments and is known to be susceptible to polioviruses 1, 2, and 3.

LLC-MK2 cells produce the protease plasminogen activator associated with the kidneys that typically initiates the process of fibrinolysis by converting plasminogen to plasmin. The cells are negative for the enzyme reverse transcriptase and exhibit epithelial morphology. They exhibit adherent growth to glass and polymer surfaces in culture.

Rhesus monkeys, like those that served as the source for the LLC-MK2 cell line, have a long history of scientific use. Found naturally throughout Southeast Asia and India, the primates have proven to be very resilient and simple to care for in captivity, making them well suited animals for experimental research. Moreover, due to their close genetic relationship to humans, they experience very similar diseases to those that affect Homo sapiens. Rhesus monkeys are especially well known for the part they played in the discovery of the Rh, or rhesus, factor, a protein present in the red blood cells of most humans that can cause severe antigenic reactions. Cell lines established from rhesus monkeys have also been important for the development of many vaccines. In fact, LLC-MK2 cells have been central in the production of mumps vaccines and are often used in the isolation of parainfluenza viruses as well.

A culture of LLC-MK2 monkey kidney cells (depicted above) was fluorescently labeled for the mitochondrial network with MitoTracker Red CMXRos, a derivative of X-rosamine. In addition, the culture was stained with Hoechst 33258, targeting DNA in the cell nucleus. Images were recorded in grayscale with a 12-bit digital camera coupled to either a Nikon E-600 or 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.