Bacterial Opsonization by SP-A Does Not Result in Differential In Vivo Phagocytosis and Killing of STM Mutants

<div><p>(A) In vitro phagocytosis assays were performed using live, GFP-expressing PA01 and isogenic <i>pch and ptsP</i> bacteria, with alveolar macrophages isolated from SP-A^+/+ mice<i>.</i> Internalized bacteria were counted using a phase contrast fluorescence microscope. The means of three experiments are shown. Two hundred macrophages were counted for each mouse. <i>p</i> = 0.0058 (PA01 vs PA01 + SP-A), <i>p</i> = 0.075 (<i>pch</i> vs <i>pch +</i> SP-A), and <i>p</i> = 0.109 (<i>ptsP</i> vs <i>ptsP +</i> SP-A).</p><p>(B) In vitro phagocytosis of PA01, <i>pch,</i> and <i>ptsP</i> by human neutrophils isolated from healthy volunteers. Phagocytosis experiments were performed as described for (A). <i>p</i> = 0.037 (PA01 vs PA01 + SP-A), <i>p</i> = 0.577 (<i>pch</i> vs <i>pch +</i> SP-A), and <i>p</i> = 0.919 (<i>ptsP</i> vs <i>ptsP +</i> SP-A).</p><p>(C–E) SP-A did not affect uptake or killing of STM mutants. PA01 (C), but not the STM mutants <i>pch</i> (D) and <i>ptsP</i> (E) were killed in significant amounts by neutrophils, independent of SP-A. The mean of three separate experiments is shown. <i>p</i> < 0.001 when comparing PA01 versus PA01 + neutrophils, and when comparing PA01-SP-A versus PA01-SP-A + neutrophils.</p>