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

Figure 8

Role of bacterial capsular polysaccharide in the modulation of CD4⁺ T cell surface expression of CD69. 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 8 h and 24 h, cells were harvested, and CD69 expression was analyzed by FACS. Cocultures incubated with medium alone or Concanavalin (0.1 μg/mL) served as negative (−) and positive controls (+), respectively. (a) Representative data from 3 different experiments. Twenty thousand gated events were acquired per sample and data analysis was performed using Cell Lab Quanta Collection/Analysis software. Quadrants were drawn based on FITC- and PE-control stains and were plotted on logarithmic scales. Numbers in the upper quadrants indicate the % of CD4⁺ CD69⁺ cells. (b) Data are expressed as means ± SEM from 3 different experimental infections; indicates statistically significant differences between cocultures infected with wild-type strain COH-1 and those infected with the nonencapsulated mutant ΔcpsE.

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