(A) Shown is an ethidium bromide stained agarose gel electrophoresis of a B. burgdorferi flagellin-specific nested PCR performed on ear tissue of humanized mice carrying the functional (232I, lanes 29–41) or non-functional (232T, lanes 1–7)) FcγRIIb alleles 2 weeks after infection with B. burgdorferi. Where indicated, humanized, infected mice were injected with B cell (α-CD20, lanes 19–28) and CD4 T cell (α-CD4, lanes 8–18) specific antibodies to deplete the respective immune cell subsets. In the first and last lanes, a size standard (std; 100 base pair ladder) was loaded. In lanes 42–43, a sample of a previous positively tested non-humanized infected mouse sample (NSG), a positive control (PK) (B. burgdorferi positive tick lysate) and a negative control (NK) were loaded as controls. (B) Presented is a table summarizing the effect of FcγRIIb alleles and B cell or CD4 T cell depletion on B. burgdorferi infection in humanized mice, including the number of positively tested animals and the calculated percentage values (in brackets). (C, D) Shown are box and whisker plots depicting the pathogen load (B. burgdorferi flaB copy numbers normalized to mouse nidogen-1 copy numbers) in ears (C) and hearts (D) of infected humanized mice treated with an isotype control (Iso) or CD20-specific antibody (α-CD20) (as described in Figure 3A) at the indicated timepoints after infection with B. burgdorferi. n = 5–7 mice per group. An unpaired Student’s t-test was used to evaluate statistical significance. *p<0.05.