CD4 and infection: Twenty-four hours after G. parasuis challenge, the proportions of CD3+ T cells, CD3+CD4+ T cells and CD3+CD8+ T cells in the blood were significantly lower in the infection group than in the control group (P < 0.05; Figure 4B, Additional file 2, panels B1, B2; Figure 5B, Additional file 3, panels B1, B2; Figure 6B, Additional file 4, panels B1, B2).