Group B Streptococcus Induces a Robust IFN-γ Response by CD4⁺ T Cells in an In Vitro and In Vivo Model

Figure 7

Role of bacterial capsular polysaccharide in the modulation of cytokine production by CD4⁺ T cells. Dendritic cells (DCs) were infected with either wild-type GBS strain COH-1 or its nonencapsulated isogenic mutant ΔcpsE (MOI:1) for 1 h. Extracellular bacteria were killed by antibiotic treatment and cultures washed prior to addition of freshly isolated splenic CD4⁺ T cells from naïve mice (T cell : DC ratio of 5 : 1). Cocultures were incubated for 48 h, resuspended in fresh medium containing 10 ng/mL of IL-2 for 72 h (resting period), and then transferred to anti-CD3 coated plates for 48 h. Supernatants were then collected and cytokines quantified by ELISA. Nonstimulated cocultures served as negative (−) controls for basal expression. Data are expressed as means ± SEM (in pg/mL) from 5 different experiments. indicates statistically significant differences compared to (−) control. indicates statistically significant differences between cocultures infected with wild-type strain COH-1 and those infected with the nonencapsulated mutant ΔcpsE.