Establishment and characterization of a Fas-resistant T cell line

Fas is a cell surface receptor that controls a signal transduction pathway leading to apoptosis. We established an antihuman Fas monoclonal antibody ( mAb)-resistant variant, kit-225-FR, from the human T cell line, kit-225. Fl ow cytometric analysis revealed that the expression of Fas molecules on kit -225-FR was preserved, The defect in Fas molecule was not detected either b y reverse transcription polymerase chain reaction (PCR) analysis of the Fas transcript or by PCR-single strand conformation polymorphism analysis of t he Fas gene in kit-225-FR. Although kit-225-FR was resistant to a high conc entration of anti-Fas-mAb, apoptosis could be induced, as with the wild typ e,by exogenous C2-ceramide exposure; MORT1/FADD was expressed at wild-type level in kit-225-FR, as determined by Western blot analysis. It therefore a ppears that the apoptotic signal transduction in kit-225-FR is defective be tween FADD and the sphingomyelin-ceramide pathway. By comparing the differe nces from the wild-type kit-225, kit-225-FR would serve as a useful cell li ne for analyzing Fas-specific signal transduction pathways in detail.