TRBC1 and infection: Although there was no significant difference between the percentage or absolute number of CD11bhighCD14+F4/80+ macrophages that express TCRβ between ECM-susceptible C57BL/6 mice and ECM-resistant Balb/c mice over the course of a Pb−A infection, the mean fluorescence intensity (MFI), a measure of the protein quantity per cell, of TCRβ-FITC was significantly higher (1.7 fold, p<0.0001, Two-way ANOVA followed by Bonferroni) in C57BL/6 (4159 ± 241) compared to Balb/c (2453 ± 224) mice on day 4 post-infection.