Fig. 7. CD47 associates with CD11b/CD18 and regulates integrin activation in human PMN.

CD47 was knocked down by CRISPR/Cas9 in the human promyelocitic cell line (HL60). HL60 and CD47-null HL60 (HL60/E2) were then differentiated into a neutrophil-like phenotype as described in the methods. a, b CD11b expression on resting, differentiated HL60 was not significantly altered by CD47 knockdown: a cell surface expression of CD11b on differentiated PMN was quantified by flow cytometry and b total CD11b content was determined by western blotting. Image shows a representative western blot and graph represents a densitometry analysis of three different assays. c CD47 and CD11b association in HL60 was assessed by PLA. Positive fluorescent signals were elicited between CD47 and CD11b Abs, as well as between CD11b and CD18 Abs indicating close association of these proteins. CD47 and CD11b Abs did not elicit fluorescent signals on HL60/E2 (CD47 null). Nuclei were counterstained with Hoechst 33342. 100x objective. Scale bars: 50 μm. d Differentiated HL60 and HL60/E2 were stimulated with fMLF (1 μM) for different times and CD11b surface expression was determined by flow cytometry. Increased surface expression of total CD11b after fMLF stimulation was not different between HL60 and HL60/E2. e, f CD11b and CD18 activation on HL60 was determined by using activation reporter mAbs, CBRM1/5 and m24 respectively. fMLF stimulation resulted in activation of CD11b and CD18 on HL60 control cells, but the magnitude was significantly reduced in HL60/E2. Data are Means ± SEM of at least three independent experiments. *p≤0.05, **p≤0.01 as determined by Two-way ANOVA analysis. No Tx (no fMLF treatment).