Abstract
Chemokine-induced chemotaxis of leukocytes is an important part of the innate immunity and has been shown to mediate inflammation in all groups of jawed vertebrates. For jawless vertebrates, hagfish leukocytes are known to show chemotaxis toward mammalian complement anaphylotoxin and Gram-negative bacteria lipopolysaccharide. However, whether chemokines mediate chemotaxis of leukocytes in jawless vertebrates has not been conclusively examined. Here, we show C-X-C motif chemokine ligand 8 (CXCL8, also named interleukin 8) of the Northeast Chinese lamprey (Lethenteron morii) (designated as LmCXCL8) induces chemotaxis in its leukocytes. We identified LmCXCL8 and found it possesses the characteristic N-terminal cysteine residues and GGR (Gly-Gly-Arg) motif. The Lmcxcl8 gene was found to be expressed in all examined tissues, and its expression was inducible in the lamprey challenged by an infectious bacterium, Pseudomonas aeruginosa. A recombinant LmCXCL8 protein elicited concentration-dependent chemotaxis in peripheral blood leukocytes isolated from the Northeast Chinese lamprey. Based on these results, we conclude that LmCXCL8 is a constitutive and inducible acute-phase cytokine that mediates immune defense and trace the chemotactic function of chemokine to basal vertebrates.
Highlights
Chemokine is a group of cytokines that induce chemotaxis of white blood cells, which is critical to the inflammatory process and innate defense against pathogens
The LmCXCL8 protein has the typical arrangement of four conserved cysteine residues as found in other chemokines (Figure 1B, positions C36, C38, C63, and C80)
Our results are consistent with the hypothesis that chemokine induces homologous chemotaxis in basal vertebrates
Summary
Chemokine is a group of cytokines that induce chemotaxis of white blood cells, which is critical to the inflammatory process and innate defense against pathogens. Chemokines have been found to play a critical role in regulating immune cell migration under both inflammatory and normal physiological conditions [3]. According to their function, chemokines can be divided into inducible or inflammatory chemokines and constitutive or homeostatic chemokines [4]. Based on the arrangement of the first two highly conserved N-terminal cysteine residues, chemokines are classified into subfamilies, CXC, CC, C, CX3C, and CX [5] Genes encoding these chemokines have been found in the genomes of all vertebrate groups. In contrast to extensive studies on functions of chemokines in jawed vertebrate [13], examination of chemokine functions was limited in basal vertebrates and invertebrates
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