FIG. 3.

Adherence of pneumococci to CR1⁺ erythrocytes is inhibited in the presence of anti-CR1 antibody. FITC-labeled Streptococcus pneumoniae BG7322 was opsonized in mouse serum and then incubated with WT mouse erythrocytes (E) or CR1⁺ mouse erythrocytes that had been pretreated with either anti-CR1 antibody 3D9 or control IgG for 1 h at room temperature. While a shift in the CR1⁺ population was present in comparison to the WT population, the shift was not observed for CR1⁺ erythrocytes pretreated with monoclonal antibody 3D9 to human CR1.