PMN secretion products mediate monocyte recruitment. (A) Number of adherent and extravasated fluorescent cells in the musculus cremaster quantified 12 hours after intrascrotal application of PAF (10⁻⁶ M) in CX3CR1^eGFP/+ mice with intact WBC (ctrl), in neutropenic mice (PMN depl), and in neutropenic mice receiving intrascrotal injection of PMN secretion (PMN depl + PMN-sec). (B) Representative FACS plots showing Gr1 versus F4/80 staining and number of PMN and monocytes in the subcutaneous air pouch of C57BL/6 mice 12 hours after injection of PAF (10⁻⁶ M) in mice with intact WBC (ctrl), in neutropenic mice (PMN depl), and in neutropenic mice where PMN secretion was injected into the pouch (PMN depl + PMN-sec). (C) Analysis of MPO activity (top) and detection of MMP-9 (bottom) in the air pouch lavage fluid of C57BL/6 mice (ctrl), neutropenic mice (PMN depl), and neutropenic mice injected with PMN secretion (PMN depl + PMN-sec). Data are expressed as means (± SD), n = 4-6 for each bar. * indicates significant difference compared with ctrl; ** indicates significant difference compared both to ctrl and PMN depl + PMN-sec.