CR2 and infection: Analysis of CD21 and CD23 levels on B cells from T. cruzi infected mice indicates that the expression of both markers decreased overall on B cells by day 8 post-infection in resistant C57Bl/6 mice, after which expression increased over the course of infection; CD21 remained relatively unchanged in susceptible Balb/c mice at day 8 and 15, then slightly increased at day 28 post-infection, while CD23 levels were decreased at every time-point analyzed (Fig 7A).