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

Figure 6

In vivo generation of memory CD4⁺ T cells during GBS infection. C57BL/6 mice were injected intraperitoneally with a dose of 10⁶ CFU of wild-type GBS serotype III strain COH-1. Surviving animals who had previously displayed clinical signs were boosted with a second dose of 10⁶ CFU of GBS strain COH-1 two weeks after initial infection. Spleens of animals with clinical signs and positive bacteremia were harvested 48 h after boost infection. Total splenocytes were stained and analyzed by multiparametric FACS. (a) Cells were gated on CD3⁺ CD4⁺ double-positive cells, followed by gating CD62L⁻ (effector [memory] T cells) and CD62L⁺ (central memory T cells). A histogram from a representative control (mock-infected) mouse was selected for the figure. (b) A fifth surface marker, IL-7Rα⁺, was used to further identify memory cells ( IL-7Rα⁺) within the CD62L⁻ (effector [memory] T cells) and CD62L⁺ (central memory T cells). IL-7Rα⁺ cells reflect memory cells within these respective populations. Histograms from representative control (mock-infected) and infected mice were selected for the figure. Thirty thousand events gated on CD3⁺ CD4⁺ cells were acquired per sample and data analysis was performed using Kaluza® Flow Analysis software.

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