DDR2 regulates neutrophil migration in 3D. (A) Neutrophil adhesion to a collagen-coated surface is not altered by rDDR treatment Human primary neutrophils were plated on collagen I–coated surfaces (treated with or without rDDR) for 30 minutes under IL-8 stimulation. Results represent the relative percentage of adhering cells (average ± SEM) of 3 independent experiments. (B) DDR inhibition does not affect neutrophil migration in 2D. Neutrophil migration to 500nM IL-8 on a collagen I–coated surface (pretreated with or without rDDR) was measured in a EZ-Taxiscan assay. Images were taken every 30 seconds for 30 minutes; 0-, 10-, and 20-minute images are presented. Also see supplemental Video 1. Results are representative of 3 independent experiments. Quantification is presented in supplemental Figure 2A. (C) rDDR treatment inhibits neutrophil migration through collagen-coated Transwells. Migration of human primary neutrophils to 500nM IL-8 or 1μM LTB₄ through collagen I–coated Transwells (pretreated of not with rDDR) was determined after 6 hours. Results represent the relative percentage of migrating cells after treatment (average ± SEM) of 4 independent experiments. *P < .05, Friedman test; Dunn posthoc test. (D) Neutrophil treatment with DDR2-blocking antibodies inhibits neutrophil migration through collagen-coated Transwells. Human primary neutrophils were pretreated for 30 minutes with blocking antibodies (or a control antibody). The number of neutrophils migrating to 500nM IL-8 through collagen I–coated Transwells (pretreated with or without rDDR) was determined after 6 hours. Results represent the relative percentage of migrating cells after treatment (average ± SEM) of 4 independent experiments. *P < .05, Friedman test; Dunn posthoc test.