We observed that during continuation of LD culture after fresh passage the parasite slowly loses its ability to infect J774A.1 When the infection into J774A.1 in average is more than or equal to three LD infection/macrophage, the increase in TfR1 is detectable, whereas less than three LD infection/macrophage shows marginal or no increase in TfR1 expression (nV-LD, Fig. 1C). This evidence concerns the gene TFRC and infection.