PMN secretion specifically activates inflammatory monocytes. (A) Migration distance of monocytes in 3 cremaster muscles of CX3CR1^eGFP/+ mice over a 30-minute period before and after superfusion with PMN secretion. Distinction between resident and inflammatory monocytes was based on their fluorescence intensity. Horizontal lines indicate group average. The difference in number of cells included in the analysis reflects the different efficacy in recruitment between the 2 monocyte subsets. (B) Leukocytes from C57BL/6 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.