Intriguingly, most abscess margin-positioned F4/80-positive macrophages co-localized with signals specific for cleaved (activated) caspase-9 indicating that wild-type staphylococci preferentially provoke induction of intrinsic apoptosis in phagocytes during infection (Figs 1I, 1J, S3C and S3D). Here, CASP9 is linked to infection.