CD4 and infection: We also analyzed the TCR usage on PBMCs in this model, and found that infection resulted in an approximately 10–15% decrease in TCR2 frequency in blood CD8+ T cells within both lines during days 8–14 of infection (p < 0.05) (Figure 6C), which may indicate tissue demand for this T cell population, while TCR frequency was not perturbed in CD4+ PBMCs of either line during this phase of infection (Figure 6D).