Lineage- and stage-specific activity of the Dβ1 promoter. Luciferase activity in lymphoid cell lines is shown for the luciferase vector alone and for the ▵2184 (−2184 to +151) Dβ1 genomic fragment in the reverse or forward orientation in constructs containing Eβ. p5424 and p4980 are Rag-deficient pro-T cell lines; EL-4 and BW5147 are characteristic of more mature stages of the T-cell lineage; WEHI 231 and A20 are B-cell lines. Results are expressed as percentage of the activity of the pGL-3 control vector containing SV40 promoter and enhancer as in Fig 4. Mean and standard error for four independent transfections are given. Differences in promoter activity between the p5424 or p4980 pro-T lines and each of the other T- and B-cell lines were statistically significant (P < .05).