FIG. 2.

TNF-α secretion, induction of naive T-cell proliferation, and IL-12 secretion by human DCs infected with smooth and rough Brucella strains. (A, B, and D) Immature human DCs were infected with B. suis WT and B. suis manB mutant (A and D) or with B. abortus WT and B. abortus 45/20 (B). Supernatants were collected at 24 h p.i. (A and D) or at different times p.i. (B) and assayed for TNF-α concentrations (A and B) or IL-12 concentrations (D). Results are means ± standard errors of the means of 15 (A and D) or 3 (B) independent experiments performed on cells from distinct donors. (C) At 24 h p.i. DCs not infected (NI) or infected with B. suis WT, B. suis manB mutant, or E. coli were tested for their abilities to stimulate allogeneic naive CD4⁺ T-lymphocyte proliferation. Coculture of infected DCs and T cells was performed at different DC/T-cell ratios for 5 days before determination of lymphoproliferation percentages by CFSE analysis. Results are means ± standard errors of the means of nine independent experiments performed on cells from nine distinct donors. Statistical differences versus Brucella WT-infected DCs are indicated (*, P < 0.05; **, P < 0.01; ***, P < 0.001, all computed by paired Student t tests).