Fibroblasts are mesenchymal cells derived from the embryonic mesoderm. They have been extensively used for a wide range of cellular and molecular studies as they are one of easiest types of cells to grow in culture. Their durability also makes them amenable to a variety of manipulations ranging from studies employing gene transfection to microinjection. In general, fibroblasts secrete a non-rigid extracellular matrix which is rich in type I and/or type III collagen. There is evidence showing that fibroblasts in various organs are intrinsically different. In the lymphoid compartment, fibroblasts construct a unique conduit system with intriguing size exclusion which plays a fundamental role in regulating immune response and homeostasis of tissue fluids. RLF from ScienCell Research Laboratories are isolated from rat lymph nodes. RLF are cryopreserved at passage one and delivered frozen. Each vial contains >5 x 105 cells in 1 ml volume. RLF are characterized by their spindle-shaped morphology and immunofluorescence with antibody specific to fibronectin. RLF are negative for mycoplasma, bacteria, yeast, and fungi. RLF are guaranteed to further expand for 5 population doublings under the conditions provided by ScienCell Research Laboratories. Recommended Medium It is recommended to use Fibroblast Medium (FM, Cat. #2301) for culturing RLF in vitro.