The spectrum of human kallikrein 6 (zyme/protease M/neurosin) expression in human tissues as assessed by immunohistochemistry

The KLK6 gene is anew member of the human kallikrein gene family and encode s for a secreted protease, human kallikrein 6 (hK6; also known as zyme/prot ease M/neurosin). No study has as yet reported detailed immunohistochemical localization of hK6 in human tissues. Our purpose was to examine the expre ssion of hK6 in human tissues by immunohistochemistry. We have analyzed 199 paraffin blocks from archival, current, and autopsy material prepared from almost every normal human tissue. We employed an hK6-specific polyclonal r abbit antibody and avidin-biotin to localize hK6 by IHC. The staining patte rn, the distribution of the immunostaining, and its intensity were studied in detail. The IHC expression of zyme was generally cytoplasmic. Various no rmal human tissues expressed the protein abundantly. Glandular epithelia co nstituted the main immunoexpression sites, with representative organs being the breast, prostate, kidney, endometrium, colon, appendix, salivary gland s, bile ducts, and gallbladder. The small intestine, stomach, endocervix, F allopian tube, epididymis, bronchus, and upper respiratory tract showed a f ocal expression as well. Choroid plexus epithelium, peripheral nerves, and some neuroendocrine cells (including the islets of Langerhans, cells in the anterior pituitary gland, and adrenal medulla) expressed the protein stron gly and diffusely. A characteristic immunostaining was observed in the Hass all's corpuscles of the thymus, the oxyphilic cells of the thyroid and para thyroid glands, the primordial follicles of the ovary, dendritic cells main ly in the spleen, and in various cells of the placenta.