Neutrophil chemotaxis is a fundamental aspect of inflammatory injury in conditions such as the Adult Respiratory Distress Syndrome (ARDS). Neutrophil chemotaxis is directly attributable to which of the following molecules?

a. C5a

e. ENA-78 (Epithelial Neutrophil Activating Protein) 

There is a large collection of peptide, polypeptide and lipid mediators which have chemotactic properties. Although TNF a, IL-1 and LPS were initially reported to have direct neutrophil chemotactic activity, recent studies have demonstrated that these molecules are not directly chemotactic for neutrophils. This finding suggests that cytokine networks may be operative in vivo and depend on the initial expression of early response cytokines. This initial interaction is followed by the generation of more distal inflammatory mediators that directly influence neutrophil chemotaxis and activation. There is a particularly important group of novel chemotactic cytokines which share significant homology with the presence of four conserved cysteine amino acid residues. These cytokines in their monomeric forms are all less than 10 kD, are characteristically basic heparin-binding proteins, have specific neutrophil chemotactic activity and display four highly conserved cysteine amino acid residues, with the first two cysteines separated by one non-conserved amino acid residue. Because of their chemotactic properties and the presence of C-X-C cysteine motif, these have been designated the C-X-C chemokine family. Twelve different chemokines have been identified in the last decade. These include IL-8, epithelial neutrophil activating protein (ENA-78), and others. Among the other endogenous chemoattractants are several complementderived peptides. Perhaps, the most potent of these is the short-lived C5a peptide