Crithidia luciliae is a flagellate parasitic protist known to use the housefly Musca domestica as a host. As part of the family of Trypanosomatidae, they are characterised by the presence of a kinetoplast; a complex network of interlocking circular dsDNA molecules. The presence of this kinetoplast means they are important in the diagnosis of systemic lupus erythamatosus (SLE). By using C.luciliae as a substrate for immunofluorescence, the organelle can be used to detect anti-dsDNA antibodies, a common feature of the disease.