Innate immunity is important for the integrity of the host against potentially invasive pathogenic microorganisms in the environment. Antibiotic peptides with broad antimicrobial activity are part of the innate immune system. We investigated the presence of the cathelicidin, human cationic antimicrobial protein (hCAP-18), in the male reproductive system. We found strong expression of the hCAP-18 gene by in situ hybridization and hCAP-18 protein, as detected by immunohistochemistry, in the epithelium of the epididymis, but not in the testis. The highest expression in the epididymis was in the caudal part. Western blotting showed a doublet band, the upper part corresponding to the size of hCAP-18 in plasma and neutrophils. Using a specific enzyme-linked immunosorbent assay (ELISA), levels of 86.5 ؎ 37.8 g/ml (mean ؎ standard deviation; range, 41.8 to 142.8 g/ml; n ‫؍‬ 10) were detected in seminal plasma from healthy donors, which is 70-fold higher than the level in blood plasma. Flow cytometry and immunocytochemistry revealed the presence of hCAP-18 on spermatozoa. ELISA measurement showed levels of 196 ng/10 6 spermatozoa, corresponding to 6.6 ؋ 10 6 molecules of hCAP-18 per spermatozoon. Our results suggest a key role for hCAP-18 in the antibacterial integrity of the male reproductive system. The attachment of hCAP-18 to spermatozoa may implicate a role for hCAP-18 in conception.The integrity of the human reproductive system against potentially invasive pathogenic microorganisms is crucial. Readily available, preformed antimicrobial proteins of the nonadaptive immune system serve as the body's first line of defense (5), while the adaptive immune system becomes involved if pathogens start to invade. In recent years, several components of the human nonadaptive immune system have been isolated and characterized, among them the only member of the cathelicidins known to exist in humans, the human cationic antimicrobial protein (hCAP-18) (4, 10). This protein is synthesized in neutrophil progenitors in the bone marrow and stored in the specific granules of mature neutrophils (15). It is synthesized as an 18-kDa proprotein from which a 5-kDa C-terminal fragment, LL-37, bearing all of the hitherto known biological activity, is cleaved (8). LL-37 has lipopolysaccharide-binding properties and manifests antibacterial effect against a wide range of bacterial species (11,20). Recently, expression of hCAP-18 has also been demonstrated in the epithelium of several organs, including the vagina, cervix, mouth, and lung (2, 6). The cDNA encoding hCAP-18 has been detected in a library prepared from the human testis, suggesting that the gene is expressed here (1).In the present study, we investigated the presence of hCAP-18 in the male reproductive system. We found expression in the epithelium of the epididymis by in situ hybridization and by immunohistochemistry. High levels of hCAP-18 were found in seminal plasma and in association with spermatozoa, but we were unable to detect expression of the hCAP-18 gene or the presence of hC...

These findings suggest that, through expression of CXCL5, eosinophils can recruit and activate CXC receptor 2 (CXCR2)-bearing cells such as neutrophils at sites of inflammation. Eosinophils may also promote connective tissue remodelling through release of this peptide.

Eosinophils participate in allergic inflammation and may have roles in the body's defense against helminthic infestation. Even under noninflammatory conditions, eosinophils are present in the mucosa of the large intestine, where large numbers of gram-negative bacteria reside. Therefore, roles for eosinophils in host defenses against bacterial invasion are possible. In a system for bacterial viable counts, the bactericidal activity of eosinophils and the contribution of different cellular antibacterial systems against Escherichia coli were investigated. Eosinophils showed a rapid and efficient killing of E. coli under aerobic conditions, whereas under anaerobic conditions bacterial killing decreased dramatically. In addition, diphenylene iodonium chloride (DPI), an inhibitor of the NADPH oxidase and thereby of superoxide production, also significantly inhibited bacterial killing. The inhibitor of nitric oxide (NO) production L-N 5 -(1-iminoethyl)-ornithine dihydrochloride did not affect the killing efficiency, suggesting that NO or derivatives thereof are of minor importance under the experimental conditions used. To investigate the involvement of superoxide and eosinophil peroxidase (EPO) in bacterial killing, EPO was blocked by azide. The rate of E. coli killing decreased significantly in the presence of azide, whereas addition of DPI did not further decrease the killing, suggesting that superoxide acts in conjunction with EPO. Bactericidal activity was seen in eosinophil extracts containing granule proteins, indicating that oxygen-independent killing may be of importance as well. The findings suggest that eosinophils can participate in host defense against gram-negative bacterial invasion and that oxygen-dependent killing, i.e., superoxide acting in conjunction with EPO, may be the most important bactericidal effector function of these cells.

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