FIG 4.

Anti-PspA^hkR36A MAbs promote pneumococcal killing by human blood in vitro. S. pneumoniae strains BG8838 (A and B) and D39 (C and D) were incubated with blood from healthy donors and purified anti-PspA^hkR36A or a matched isotype control MAb. Matched IgG1 and IgG2a isotype control MAbs were used as the comparator in panels A and C and B and D, respectively (not shown). The contents were rotated for (3 h for BG8838 and 2 h for D39) at 37°C, and the surviving pneumococci were enumerated by plating. The identity of the anti-PspA^hkR36A MAb and the percent killing are plotted on the x and y axes, respectively. The percent bacterial killing was calculated as described in Materials and Methods. The assay was performed at least four times, and data from a single representative experiment are shown.