Fig. 1. Expression of death receptors, death ligands and their signalling molecules in thymocyte subsets. (A) Pro–T3, pro–T4, pre–T (divided into large and small cells on the basis of their forward light scatter) and thymic stromal cells from 6- to 10-week-old rag–1^–/– and FADD–DN rag–1^–/– mice were analysed for the presence of specific RNA transcripts by RT–PCR. PCR was performed on 5–fold serial dilutions of cDNA and the amplification products were probed with a ³²P–labelled internal oligonucleotide. (B and C) Pro–T3, pro–T4 and pre–T cells from FADD–DN rag–1^+/+ mice (B) and pro–T cells from FADD–DN rag–1^–/– mice (C) were analysed for FADD–DN expression by cytoplasmic immunofluorescence and flow cytometry using anti-FLAG antibody. Solid lines represent FADD–DN transgenic cells and dotted lines represent wild-type (B) or rag–1^–/– (C) cells. Profiles are representative of analyses of three mice of each genotype.