ICOS and infection: In the CD4+CXCR5+T, ICOS+ TFH, ICOS+PD−1+ TFH cells, non post infection group was higher than post infection group, but there were no significant differences (P = 0.5036, 0.5541, 0.4556, Figures 2(g), 2(h), and 2(j)); in the PD-1+ TFH cells, non post infection group was lower than post infection group, but there were no significant differences (P = 0.0759, Figure 2(i)).