Neutrophil inhibitory factor (NIF) of the dog hookworm, Ancylostoma caninum, is a 41 kDa secreted glycoprotein that is thought to allow the hookworm to evade the innate immune defenses of the host (1, 2). NIF interacts with the leukocyte integrin alpha M beta 2 (CD11b/CD18, also called Mac-1), thus inhibiting mammalian neutrophil adhesion to endothelium (1). The A. caninum NIF cDNA encodes 257 amino acids (aa) including a 17 aa signal sequence and a 240 aa mature protein with 10 cysteine residues and 7 potential N-linked glycosylation sites (1). Incubation of mammalian neutrophils with NIF does not appear to be toxic, but does result in rapid, cation‑dependent, reversible inhibition of alpha M beta 2-mediated adhesion and degranulation (1 - 4). The NIF binding site within the alpha M beta 2 I-domain interferes with activation‑dependent adhesion sites of ligands including ICAM-1/CD54, complement component C3b, and fibrinogen (2, 3). In mouse or guinea pig inflammatory lung injury models, administration of NIF prevented neutrophil-dependent vascular injury (4, 5).
| Uniprot | A. caninum |
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