Immunofluorometric assay of human kallikrein 10 and its identification in biological fluids and tissues

Background: The human kallikrein 10 gene [KLK10, also known as normal epith elial cell-specific 1 gene (NES1)] is a member of the human kallikrein gene family. The KLK10 gene encodes for a secreted serine protease (hK10). We h ypothesize that hK10 is secreted into various biological fluids and that it s concentration changes in some disease states. The aim of this study was t o develop a sensitive and specific immunoassay for hK10. Methods: Recombinant hK10 protein was produced and purified using a Pichia pastoris yeast expression system. The protein was used as an immunogen to g enerate mouse and rabbit polyclonal anti-hK10 antisera. A sandwich-type imm unofluorometric assay was then developed using these antibodies. Results: The hK10 immunoassay has a detection limit of 0.05 mug/L. The assa y is specific for hK10 and has no detectable cross-reactivity with other ho mologous kallikrein proteins, such as prostate-specific antigen (hK3), huma n glandular kallikrein 2 (hK2), and human kallikrein 6 (hK6). The assay was linear from 0 to 20 mug/L with within- and between-run CVs < 10%. hK10 is expressed in many tissues, including the salivary glands, skin, and colon a nd is also detectable in biological fluids, including breast milk, seminal plasma, cerebrospinal fluid, amniotic fluid, and serum. Conclusions: We report development of the first immunofluorometric assay fo r hK10 and describe the distribution of hK10 in biological fluids and tissu e extracts. This assay can be used to examine the value of hK10 as a diseas e biomarker. (C) 2001 American Association for Clinical Chemistry.