Identification of Defensin-1, Defensin-2, and CAP37/Azurocidin as T-cell Chemoattractant Proteins Released from Interleukin-8-stimulated Neutrophils

Abstract

Reports that interleukin-8 (IL-8) induces the infiltration of neutrophils followed by T-cells into injection sites led us to postulate that by stimulation of neutrophil degranulation IL-8 may cause the release of factors with chemoattractant activity for T-lymphocytes. Extracts of human neutrophil granules were chromatographed to isolate and purify T-lymphocyte chemoattractant factors. Two major peaks of T-cell chemotactic activity were purified by C18 reversed phase high pressure liquid chromatography (HPLC). The first peak was resolved further by C4 reversed phase HPLC and yielded an active fraction shown by NH 2 -terminal amino acid sequence analysis to contain defensins HNP-1, HNP-2, and HNP-3. Purified defensins HNP-1 and HNP-2 (kindly provided by Dr. R. I. Lehrer, UCLA) were also potent chemoattractants for human T-cells, while HNP-3 was inactive. The second peak of T-cell chemoattractant activity was also further purified to homogeneity by C4 reversed phase HPLC and identified by NH 2 -terminal sequence analysis as CAP37/azurocidin, a protein with sequence homology to serine proteases. 0.1-100 ng of defensins and 1.0 -100 ng/ml CAP37 were able to stimulate in vitro T-cell chemotaxis. Neutrophil activating factors, i.e. IL-8, phorbol 12-myristate 13-acetate/ionomycin, and formylmethionylleucylphenylalanine each induced the release of CAP37 and defensins from neutrophil granules. Subcutaneous administration of defensins or CAP37/azurocidin into BALB/c mice resulted in a moderate neutrophil and mononuclear cell infiltrate by 4 h, which was greater by 24 h at the site of injection. Additionally, subcutaneous injection of defensins into chimeric huPBL-SCID mice resulted in significant infiltration by human CD3؉ cells within 4 h. These results identify the antimicrobial proteins, CAP37/azurocidin and defensins HNP-1 and HNP-2, as potent neutrophil-derived chemoattractants for T-cells. These proteins represent primordial antimicrobial peptides which may have evolved into acute inflammatory cell-derived signals that mobilize immunocompetent Tcells and other inflammatory cells.

Peptides as toxins/defensins

“…These peptides appear to have had an active role in the transition to the adaptive immune response (Chertov et al 1996). Although AMPs may act directly on microbial cells by damaging or destabilizing the cell membrane, they seem to be involved in the organization of the innate immune and inflammatory responses (Hancock and Diamond 2000).…”

A Potent and Selective Nonpeptide Antagonist of CXCR2 Inhibits Acute and Chronic Models of Arthritis in the Rabbit

“…Since CXCR2 is expressed by a number of leukocyte subsets in addition to neutrophils, including monocytes, macrophages, dendritic cells, T cells, NK cells, and basophils (50 -52), it is possible that the CXCR2 antagonist directly inhibits ELR ϩ chemokine-induced mononuclear cell infiltration into the joint (53). Alternatively, the antagonist may directly inhibit only neutrophil chemotaxis and/or degranulation, thereby preventing the release of mediators such as defensins, CAP37/azurocidin and cathepsin G, which function as chemotactic agents for T cells and monocytes (54,55). Consistent with the latter explanation is the fact that in each of the arthritis models described, neutrophils are the first cell type to accumulate in the synovial fluid, followed sequentially by monocytes and lymphocytes (data not shown).…”

Hypoxic regulation of neutrophil function and consequences for Staphylococcus aureus infection

“…They can release both pro-and anti-inflammatory cytokines in an agonist-dependent manner [16], secrete products such as defensins and cathelicidins which induce CD4 þ and CD8 þ T cell chemotaxis [17], and acquire certain properties of antigen presenting cells [18]. Although these attributes confer a more complex, flexible and environmentspecific role than previously appreciated, the key neutrophil function remains host defence against invading pathogens, and when this function is significantly compromised, severe infection is more likely.…”