Effect of capsular polysaccharide on the capacity of DCs to internalize S. suis. Bacteria (MOI: 1) were either non-opsonized or pre-opsonized with 20% complete normal pig serum for 30 min prior to incubation with DCs for 30 min, 60 min, 90 min, 2 h and 4 h. Numbers of internalized bacteria were determined by quantitative plating after 1 h of antibiotic treatment, and the results are expressed as CFU recovered bacteria per mL (means ± SEM obtained from independent experiments using DCs derived from nine different animals. Experiments were repeated at least three independent times). *p < 0.05, indicates statistically significant differences between the wild-type strain 31533 and its isogenic non-encapsulated mutant either non-opsonized or pre-opsonized with complete normal pig serum. WT, wild-type strain. CPS-, non-encapsulated mutant.