This line was originally established by M. Rollinghoff and N.L. Warner from a fibrosarcoma induced by subcutaneous injections of 3-methylcholanthrene. After pretreatment with actinomycin D, the cells are highly sensitive to human cytotoxic monocytes, to human tumor necrosis factor and to lymphotoxin. They can be used as target cells for short term chromium release cytotoxicity assays. Tested and found negative for ectromelia virus (mousepox).