Fig. 2. Identification of a putative GPR97-ligand in a distinct human neutrophil subpopulation that is activated upon interaction with GPR97^E-mFc.

a Schematics of GPR97 receptor and GPR97^E-mFc probe. b List of cell samples screened for the expression of GPR97 and the putative GPR97-ligand. * indicates a subpopulation of primary human neutrophils. c A representative bimodal surface expression profile of the GPR97-ligand in human neutrophils detected by the GPR97^E-mFc probe. d Highly variable GPR97-ligand⁻ (blue) and GPR97-ligand⁺ (pink) neutrophil subsets in bloods of different donors (samples A to N). e, f Morphological changes of neutrophils induced by GPR97^E-mFc as observed by inverted light microscope e and Wright-Giemsa stain f. Scale bar, 20 μm. Experiments were repeated 3 times with similar results. g–j Phenotypic analyses of activated neutrophils induced by GPR97^E-mFc included up-regulated ROS production g, MPO activity (h, n = 6), expressional changes of specific CD markers (i, n = 7 for CD54 and n = 4 for others) and IL-8 production (j, n = 3) of independent samples. The mFc protein and fMLF were used as a negative and a positive control, respectively. Data are presented as means ± SEM and p value was determined by two-way ANOVA in h, j and one-way ANOVA in i. Source data are provided in the Source Data file.