Recruitment of inflammatory monocytes by PMN secretion is CCR2-dependent. (A) Recruitment of Gr1⁺ inflammatory monocytes in the air pouch of CX3CR1^eGFP/eGFP mice (top) and CCR2^−/− (bottom) mice 12 hours after stimulation with PAF (10⁻⁶ M). Analyses were made in mice with intact WBC count (ctrl), neutropenic mice (PMN depl), and neutropenic mice treated with PMN secretion (PMN depl + PMN-sec). Note the difference in scale between the charts. ** indicates significant difference compared with both ctrl and PMN depl + PMN-sec. (B) Leukocytes from CCR2^−/− mice were harvested by cardiac puncture and intracellular Ca²⁺ mobilization was measured in resident monocytes (Gr1⁻, F4/80⁺, top) and inflammatory monocytes (Gr1⁺, F4/80⁺, bottom) after stimulation with medium (ctrl), ionomycin, or PMN secretion (PMN-sec). Data were acquired before and at 30-second intervals after stimulation (time = 0) and presented as average of 4 to 6 analyses for each data point. * indicates significant difference between treatment with PMN secretion and control.