In vitro activity: Leukadherin‐1 (LA1) modulates natural killer (NK) cell inflammatory cytokine secretion. The SLE-associated CD11b‐R77H variant does not influence NK cell response to Leukadherin-1. Leukadherin-1 does not modulate Syk activation in NK cells. Leukadherin-1 does not modulate Syk activation in NK cells. Leukadherin-1 (LA1) does not modulate signal transducer and activator of transcription (STAT)-4 phosphorylation. Leukadherin-1 modulates TLR-2 and TLR-7/8-induced monocyte cytokine secretion.

Kinase Assay: Leukadherin-1, also known as LA1, is a novel and specific agonist of Complement receptor 3 (CR3) and the leukocyte surface integrin CD11b/CD18 that enhances leukocyte adhesion to ligands and vascular endothelium and thus reduces leukocyte transendothelial migration and influx to the injury sites. Complement receptor 3 (CR3, CD11b/CD18) is a multi-functional receptor expressed predominantly on myeloid and natural killer (NK) cells. Leukadherin-1 (LA1) does not modulate signal transducer and activator of transcription (STAT)-4 phosphorylation. Leukadherin-1 modulates TLR-2 and TLR-7/8-induced monocyte cytokine secretion. Targeting leukocyte trafficking using LA1, an integrin agonist, is beneficial in preventing lung inflammation and protecting alveolar and vascular structures during hyperoxia. Thus, targeting integrin-mediated leukocyte recruitment and inflammation may provide a novel strategy in preventing and treating BPD in preterm infants.

Cell Assay: Supernatant cytokines are quantified after stimulation and culture for 18 h (monocytes) or 24 h (NK cells). Except for bead-based stimulation, all experiments are conducted using 100 μL cells in a 96-well plate format. NK cell stimuli are added as follows: (1) Syk inhibitor (1 μM), (2) Leukadherin-1 or dimethylsulphoxide (DMSO) (vector control) (7.5 μM). Shown to induce~82% of maximum response with negligible off-target effect, (3) anti-CD210 or isotype control (5 μg/mL), (4) 30-45 min after Leukadherin-1 NK cells are stimulated with combinations of IL-12 (10 ng/mL), IL-15 (30 ng/mL) or IL-18 (10 ng/mL): either IL-12 + IL-15 or IL-12 + IL-18. Monocytes are stimulated using pam3csk4 (TLR-2 agonist, 300 ng/mL) or R848 (TLR-7/8 agonist, 2 μg/mL). Supernatants are stored at –80oC for < 1 month before quantification. To exclude non-specific Leukadherin-1-mediated cytotoxicity, the cell viability is assayed at 24 h using the CellTitre-Glo reagent. No significant loss of viability in comparison with the DMSO control is seen, concurring with published data in other cell types.