A144E TACI is expressed and binds ligand but does not signal in 293T cells. (A) Aligned amino acid sequence of the transmembrane domains of human and mouse TACI. (B) Surface expression and BAFF binding of WT and A144E mTACI in transfected 293T cells. Similar results were obtained in 2 independent experiments. Numbers in the insets represent percentage of cells expressing TACI. Shaded histograms represent isotype controls. (C) NFκB-driven luciferase activity in 293T cells transfected with human A181E and murine A144E TACI mutants and the corresponding WT TACI. Columns and bars represent mean and SD of 3 independent experiments. The Student t test was used to calculate significance.