Thus, we examined all of the infants collectively (n = 14) but found no evidence that the percentage of CD4+ T cells in peripheral blood that were proliferating (intracellular Ki-67+ expression) or expressed CCR5 on their surface correlated with the number of challenges to infection (r = 0.45, P = 0.11; r = −0.29, P = 0.32, respectively) (Fig. 9A and B). Here, MKI67 is linked to infection.