FIGURE 9.

Model. (1) LLO monomers secreted by L. monocytogenes bind to the neutrophil plasma membrane and oligomerize into prepore complexes. (2) LLO prepore complexes undergo conformational changes to form pores, which creates an influx of Ca²⁺. (3) The rise in intracellular Ca²⁺ activates granule exocytosis at the forming phagocytic cup. Degranulation also occurs into the phagosome. Neutrophil MMP-8 rapidly degrades extracellular and intraphagosomal LLO. We propose that these actions inhibit LLO-mediated escape, trapping L. monocytogenes in a bactericidal phagosome. (4) Degranulation is linked to increased endocytosis in neutrophils. Endocytosis of LLO pores may also protect neutrophils from LLO-mediated membrane damage.