Cytokine secretion by PBMCs after 24 h co-culture with L. plantarum strains. IL-10 (A) and IL-12 (B) production and the IL-10/IL-12 ratio (C) by peripheral blood mononuclear cells (PBMCs) derived from blood of 3 different healthy donors after stimulation with 42 different L. plantarum strains harvested in stationary-phase. The L. plantarum strains grown and prepared on separate days constitute set 1 and set 2. PBMCs isolated from donor A were inoculated with L. plantarum culture set 1 (A-1) and PBMCs from donor B were inoculated with the L. plantarum replicate set 2 (B-2). PBMCs from Donor C received both sets of cultures and the mean of the IL-10 and IL-12 amounts induced by these cultures is shown. Each symbol represents a different L. plantarum strain or the PBS or LPS controls.