Figure 6. Anti-MLP IgG Promotes Killing of E. coli In Vitro and In Vivo.

(A) Neutrophil killing of WT or ΔMLP E. coli that were opsonized with PBS, WT, or J_H^−/− serum (fold of killing over killing of non-opsonized E. coli).

(B) 5 × 10⁷ CFU WT or ΔMLP E. coli were i.p. injected into 8-week-old WT mice and harvested 6 hr later to analyze surface IgG or IgA by flow cytometry.

(C and D) WT mice of 6–8 weeks were i.p. injected with 5 × 10⁷ CFU WT and or ΔMLP E. coli. The absolute numbers of monocytes/macrophages (CD11b⁺LY6C⁺LY6G^lo), neutrophils (CD11b⁺LY6G^hi), T cells (CD3⁺), and B cells (B220⁺) were determined by flow cytometry at 24 hr after infection (C). Bacterial numbers of E. coli in spleens and livers were determined at 24 hr (D). Each dot represents one mouse.

(E) WT and ΔMLP E. coli were incubated with anti-MLP or isotype-matched control IgG for 30 min. The bacterial numbers of IgG-coated bacteria were determined by flow cytometry.

(F) Survival of J_H^−/− mice that were administered 1 mg of monoclonal anti-MLP IgG or isotype 24 hr prior to i.p. infection with 10⁷ of ECM6L4 (isotype n = 7; anti-MLP n = 10).

Data represent two to three independent experiments. Error bars indicate SD. *p < 0.05, **p < 0.01, ***p < 0.001. See also Figure S5.