Figure 8

Spleens from S. suis-infected mice show reduced numbers of CD4⁺ T cells concurrently with histopathological changes, as compared to control mice.

Mice were infected intraperitoneally with a dose of 1 × 10⁷ CFU of S. suis wild-type strain P1/7. Non-infected control animals were also included. (a) At 8 days post-primary infection, % of CD3⁺CD4⁺ T cells in the spleens of infected and control animals were evaluated by FACS. Representative data (left) and individual mouse data (right) are presented from 3 experimental infections (n = 12). FACS was performed using a Cell Lab Quanta^TM SC MPL MultiPlate Loader instrument. 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-Cy5-control stains and were plotted on logarithmic scales. (b) In parallel to FACS analysis, half-spleens were preserved in formalin for histopathological analysis. Spleen sections from infected animals were compared to controls and the level of lymphoid depletion (lymphatic nodules – asterisks), granulopoiesis (white arrows), and extramedullary hematopoiesis (black arrows) was evaluated on a 4-grade scale (grade 4 being the most severe). 2.5X images (top panel) show a reduction in the number and cellularity of lymphatic nodules. 10X images (bottom panel) show an increase in extramedullary hematopoiesis as well as in granulopoiesis.