Recovery of APRIL-induced IgA production by activation of PKA in the absence of TACI. Controller TACI siRNA-transfected B cells were cultured with different doses of cAMP analog 8-bromo-cAMP (A; 10, 100 or 500 μM) (B; 500 μM) for 2 hours. Cells were further cultured in the presence of APRIL (8 μg/mL), anti-BCR antibodies (anti-Igκ and anti-Igλ, 0.5 μg/mL each), and TGF-β (1 ng/mL). PKA phosphorylation by immunoblotting (A) or IgA secretion by ELISA (B) was evaluated after 45 minutes or 10 days culture, respectively. Data are mean ± SD. *P < .05. Data are representative of 3 independent experiments with similar results.