Pro-inflammatory cytokine production in cultured PBMC is positively correlated with levels of serum H1N1-specific IgG3. Frozen PBMC (106 cells/ml), isolated from the peripheral blood at t0, were thawed and cultured with H1N1 (2 μg), for 3 days. At the end of this time, supernatants were collected and analyzed in ELISA for cytokine production. Correlations were calculated by Pearson’s test, using GraphPad Prism 5 software. P values are indicated for each graph. The numbers of individuals are given in Table 1.