TACI isoform intracellular signaling leads to NF-κB activation. (A) Confocal microscopy of A20 nontransduced cells, A20 with GFP, TACI short or long isoforms, and nonsignaling TACI S194X mutant cells. After 6 hours of starving (baseline), 1 × 106 cells were cultured for 50 minutes in complete RPMI 1640 medium in the presence or absence of 100 ng/mL of rhAPRIL, and stained for p65 (red); nuclei were counterstained with DAPI (blue). Images show white dividing lines for cells taken from the same field. Original magnification ×63. (B) Quantitative assessment of p65 expression (relative to cell number), represented as p65 relative intensity, for each condition. For quantitation of total p65, >200 cells were microscopically assessed and analyzed with ImageJ software. The mean percentage and standard error were calculated from 3 independent experiments; Error bars represent standard error of the mean. *P < .05; **P < .01; 2-tailed unpaired Student t test.
