Adherence of high-binders, but not low-binders, is reduced by blocking CbpA or C3. Solid bars, negative control; open bars, bacteria pre-treated with anti-CbpA antibody; dotted bars, A549 cells pre-treated with anti-C3 antibody. Negative control A549 cells pre-treated with normal rabbit serum. All values are mean ± one standard deviation, based on three independent experiments. Mean values are above each bar. The Y-axis units differ on graphs 1A and 1B. 1A. High-binding S. pneumoniae are identified by serotype along X-axis. 6301 evolved, 3 evolved, and 18C evolved are high-binding descendants of low-binding parent strains. Isolates identifed as 6 B all share that serotype but have different PFGE patterns. 1B. Low-binding S. pneumoniae strains are identified by serotype along X-axis. 6301 parent, 3 parent, and 18C parent are initial low-binding strains of 6301 evolved, 3 evolved, and 18C evolved.