letter to the editor 0022-1554/92/$3.30
Vol. 40. No. 11. pp. 1805-1806. 1992 Printed m U.S.A.
The Journal of Histochemistry and Cytochemistry Copyright 0 1992 by The Histochemical Society. Inc.
Letter to the Editor
I
1 Liver Metallothionein in the Lacrimal Gland
In his exhaustive study on the antigenic profile of the human lacrimal gland, Dr. Kivela (5) concludes that acinar myoepithelial cells and ductal basal cells differ considerably. The former were found to express vimentin. a-smooth muscle actin, and glial fibrillary acid protein (GFAP). whereas the latter were labeled by antibodies directed to cytokeratins 5, G, and 13. In accordance with data from the salivary glands, both myoepithelial and ducral basal cells were found to share only one antigen, cytokeratin 14 (5). We would like to add our recent finding that both types of cells in the human lacrimal gland share another feature, i.e.. their intense immunoreactivity for human liver metallothionein (MT). We used monoclonal antibody L2E3 raised against purified human MT-1 and MT-2, the two isoforms of MT that were isolated from the cytosol fractions of human fetal liver. Mouse monoclonal antibody L2E3 belongs to the IgGl subclass and reacts in a direct ELISA with both MT-1 and MT-2: it does not detect renal MT and does not cross-react with rabbit, rat or mouse MT (10).
Using this antibody in a three-step indirect immunoperoxidase method on acetone-fixed cryostat sections of human main and accessory lacrimal glands, two types of cells were stained (Figure 1). In the rerminal secretory end-piece, L2E3 identified the cell processes (and sometimes the nuclei) of elongated cells that completely surrounded acini and were situated between acinar epithelium and basal lamina. Immunostaining of serial frozen sections confirmed that these slender, branching cells corresponded to myoepithelial cells, since they also showed immunoreactivity for smooth muscle actin, vimentin, and GFAP. Staining for cytokeratin 14 revealed intense reactivity of myoepithelial cells and slight positivity in the acinar epithelium. Spindled cells with similar morphology and immunophenotype were also found around intercalated ducts, albeit in smaller numbers. A second type of immunoreactivity was observed in the interlobular ducts of lacrimal glands (Figure 1). Here, monoclonal antibody L2E3 stained the cytoplasm of small, cuboidal cells that were basally located, whereas the columnar, luminal ductal epithelium was distinctly negative. On serial
Figure 1. Serial frozen sections of human main lacrimal gland, stained with (a) monoclonal antibody L2E3, detecting fetal liver MT; (b) CKBl (Sigma Chemical Co.; Brussels, Belgium). detecting cytokeratin 14; and (c) 1A4 (Sigma), detecting smooth muscle actin. (a) Positivity for fetal liver MT is restricted to myoepithelial cells and basal cells in the interlobular duct (ILD),whereas (b) staining for cytokeratin 14 in addition yields weak positivity in the cytoplasm of acinar and ductal cells. (c) Staining for smooth muscle actin is restricted to vessel walls and myoepithelial cells. Three-step indirect immunoperoxidase method, lightlycounterstained with Mayer's haematoxylin. Original magnification x 275. Bar = 20 wm. 1805 Downloaded from jhc.sagepub.com at UNIV OF NEW ORLEANS on May 29, 2015
LE’ITER TO THE EDITOR
1806
frozen sections, all columnar epithelial cells but only part of the basal cells expressed cytokeratin 14; L2E3’ basal cells did not contain smooth muscle actin or GFAP. These data suggest that liver MT, as detected by monoclonal antibody L2E3, appears to be a highly sensitive marker of ductal basal or “reserve” cells. Initial screening of frozen sections from other organs containing myoepithelial cells, e.g., salivary and mammary glands, has yielded identical results, indicating that mondonal antibody L2E3 serves as a general marker of myoepithelialcells and ductal basal cells. L2E3 differs from other monoclonal antibodies directed towards myoepithelium (1,6) in that it does not react with cytokeratin peptides. Both myoepithelial and ductal basal cells are generally thought to play a role in the development of various salivary gland tumors, including pleomorphic adenoma (2.4.8). In line with this, our preliminary studies on various salivary gland tumors have revealed that neoplastic myoepithelial and ductal basal cells do not lose liver MT, indicating that immunohistochemical staining for this antigen may have a role in tumor diagnosis. The significanceof MT in myoepithelial cells and ductal basal cells is as yet unclear. MTs are a group of low molecular weight intracellular proteins that have a high affinity for essential metals such as zinc and copper, as well as for non-essential metals such as cadmium and mercury, and may therefore serve in the intracellular storage, transport and metabolism of essential metals (3). During rapid growth and increased cellular metabolic activity, zinc is required for the synthesis and metabolism of proteins and nucleic acids (9). In view of the proliferative potential of myoepithelial (7) and ductal basal cells (2) in inflammatory, regenerative, and neoplastic conditions, MT might well serve as intracellular zinc storage protein in these cells. VAN DEN Oom KRISTINAVAN H o m MARC DE LEY Department of Pathology, Laboratory of Histo- and Cytochemistry, and Department of Chemistry, Laboratory for Biochemistry Catholic University of Leuven B-3000 Lcuven. Belgium
JOOST J.
Received for publication June 17, 1992; accepted July 3, 1992 (2L2722).
Literature Cited 1. Dairkee SH, Blayney C, Smith IS, Hackett AJ: Monoclonal antibo Y
that defines humanmyoepithelium. Proc Natl Acad Sci USA 82:7409, 1985 2. Eversole LR: Histogenic classification of salivary tumors. Arch Pathol Lab Med 92:433, 1971 3 Kagi JHR, Nordberg M, eds. Metallothionein.Basel. Birkhauser-Verlag, 1979, 48 4. Kahn HJ, Baumal R, Marks A, Dardick I, van Nostrand AWP: Myoepithelial cells in salivary gland tumors. Arch Pathol Lab Med 109:190, 1985 5. Kivela T: Antigenic profile of the human lacrimal gland. J Histochem Cytochem 40:629, 1992 6. Nagle RB, Bocker W, Davis JR, Heid H W ,Kaufmann M, Lucas DO, Jarasch E-D: Characterization of breast carcinomas by two monoclonal antibodies distinguishing myoepithelial from luminal epithelial cells. J Histochem Cytochem 34:869, 1986 7. Raubenheimer EJ: The myoepithelial cell. Embryology, function and proliferative aspects. Crit Rev Clin Lab Sci 25:161, 1987 8. Ragezi JA, Batsakis J G Histogenesis of salivary gland neoplasms. Otolaryngol Clin North Am 10:297, 1977 9. Valle BL, Galdes A The metalobiochemisuy of zinc enzymes. In Meister A, ed. Advances in enzymology and related areas of molecular biology. New York, Wiley & Sons, 1984, 283 10. Van Houdt K, Nicasi I. Van Mechelen E, VeulemansB, De Ley M: Monoclonal antibodies against metallothioneins from the human liver. Immunol Lett 32:21, 1992
Downloaded from jhc.sagepub.com at UNIV OF NEW ORLEANS on May 29, 2015
Vol. 40. No. 11. pp. 1805-1806. 1992 Printed m U.S.A.
The Journal of Histochemistry and Cytochemistry Copyright 0 1992 by The Histochemical Society. Inc.
Letter to the Editor
I
1 Liver Metallothionein in the Lacrimal Gland
In his exhaustive study on the antigenic profile of the human lacrimal gland, Dr. Kivela (5) concludes that acinar myoepithelial cells and ductal basal cells differ considerably. The former were found to express vimentin. a-smooth muscle actin, and glial fibrillary acid protein (GFAP). whereas the latter were labeled by antibodies directed to cytokeratins 5, G, and 13. In accordance with data from the salivary glands, both myoepithelial and ducral basal cells were found to share only one antigen, cytokeratin 14 (5). We would like to add our recent finding that both types of cells in the human lacrimal gland share another feature, i.e.. their intense immunoreactivity for human liver metallothionein (MT). We used monoclonal antibody L2E3 raised against purified human MT-1 and MT-2, the two isoforms of MT that were isolated from the cytosol fractions of human fetal liver. Mouse monoclonal antibody L2E3 belongs to the IgGl subclass and reacts in a direct ELISA with both MT-1 and MT-2: it does not detect renal MT and does not cross-react with rabbit, rat or mouse MT (10).
Using this antibody in a three-step indirect immunoperoxidase method on acetone-fixed cryostat sections of human main and accessory lacrimal glands, two types of cells were stained (Figure 1). In the rerminal secretory end-piece, L2E3 identified the cell processes (and sometimes the nuclei) of elongated cells that completely surrounded acini and were situated between acinar epithelium and basal lamina. Immunostaining of serial frozen sections confirmed that these slender, branching cells corresponded to myoepithelial cells, since they also showed immunoreactivity for smooth muscle actin, vimentin, and GFAP. Staining for cytokeratin 14 revealed intense reactivity of myoepithelial cells and slight positivity in the acinar epithelium. Spindled cells with similar morphology and immunophenotype were also found around intercalated ducts, albeit in smaller numbers. A second type of immunoreactivity was observed in the interlobular ducts of lacrimal glands (Figure 1). Here, monoclonal antibody L2E3 stained the cytoplasm of small, cuboidal cells that were basally located, whereas the columnar, luminal ductal epithelium was distinctly negative. On serial
Figure 1. Serial frozen sections of human main lacrimal gland, stained with (a) monoclonal antibody L2E3, detecting fetal liver MT; (b) CKBl (Sigma Chemical Co.; Brussels, Belgium). detecting cytokeratin 14; and (c) 1A4 (Sigma), detecting smooth muscle actin. (a) Positivity for fetal liver MT is restricted to myoepithelial cells and basal cells in the interlobular duct (ILD),whereas (b) staining for cytokeratin 14 in addition yields weak positivity in the cytoplasm of acinar and ductal cells. (c) Staining for smooth muscle actin is restricted to vessel walls and myoepithelial cells. Three-step indirect immunoperoxidase method, lightlycounterstained with Mayer's haematoxylin. Original magnification x 275. Bar = 20 wm. 1805 Downloaded from jhc.sagepub.com at UNIV OF NEW ORLEANS on May 29, 2015
LE’ITER TO THE EDITOR
1806
frozen sections, all columnar epithelial cells but only part of the basal cells expressed cytokeratin 14; L2E3’ basal cells did not contain smooth muscle actin or GFAP. These data suggest that liver MT, as detected by monoclonal antibody L2E3, appears to be a highly sensitive marker of ductal basal or “reserve” cells. Initial screening of frozen sections from other organs containing myoepithelial cells, e.g., salivary and mammary glands, has yielded identical results, indicating that mondonal antibody L2E3 serves as a general marker of myoepithelialcells and ductal basal cells. L2E3 differs from other monoclonal antibodies directed towards myoepithelium (1,6) in that it does not react with cytokeratin peptides. Both myoepithelial and ductal basal cells are generally thought to play a role in the development of various salivary gland tumors, including pleomorphic adenoma (2.4.8). In line with this, our preliminary studies on various salivary gland tumors have revealed that neoplastic myoepithelial and ductal basal cells do not lose liver MT, indicating that immunohistochemical staining for this antigen may have a role in tumor diagnosis. The significanceof MT in myoepithelial cells and ductal basal cells is as yet unclear. MTs are a group of low molecular weight intracellular proteins that have a high affinity for essential metals such as zinc and copper, as well as for non-essential metals such as cadmium and mercury, and may therefore serve in the intracellular storage, transport and metabolism of essential metals (3). During rapid growth and increased cellular metabolic activity, zinc is required for the synthesis and metabolism of proteins and nucleic acids (9). In view of the proliferative potential of myoepithelial (7) and ductal basal cells (2) in inflammatory, regenerative, and neoplastic conditions, MT might well serve as intracellular zinc storage protein in these cells. VAN DEN Oom KRISTINAVAN H o m MARC DE LEY Department of Pathology, Laboratory of Histo- and Cytochemistry, and Department of Chemistry, Laboratory for Biochemistry Catholic University of Leuven B-3000 Lcuven. Belgium
JOOST J.
Received for publication June 17, 1992; accepted July 3, 1992 (2L2722).
Literature Cited 1. Dairkee SH, Blayney C, Smith IS, Hackett AJ: Monoclonal antibo Y
that defines humanmyoepithelium. Proc Natl Acad Sci USA 82:7409, 1985 2. Eversole LR: Histogenic classification of salivary tumors. Arch Pathol Lab Med 92:433, 1971 3 Kagi JHR, Nordberg M, eds. Metallothionein.Basel. Birkhauser-Verlag, 1979, 48 4. Kahn HJ, Baumal R, Marks A, Dardick I, van Nostrand AWP: Myoepithelial cells in salivary gland tumors. Arch Pathol Lab Med 109:190, 1985 5. Kivela T: Antigenic profile of the human lacrimal gland. J Histochem Cytochem 40:629, 1992 6. Nagle RB, Bocker W, Davis JR, Heid H W ,Kaufmann M, Lucas DO, Jarasch E-D: Characterization of breast carcinomas by two monoclonal antibodies distinguishing myoepithelial from luminal epithelial cells. J Histochem Cytochem 34:869, 1986 7. Raubenheimer EJ: The myoepithelial cell. Embryology, function and proliferative aspects. Crit Rev Clin Lab Sci 25:161, 1987 8. Ragezi JA, Batsakis J G Histogenesis of salivary gland neoplasms. Otolaryngol Clin North Am 10:297, 1977 9. Valle BL, Galdes A The metalobiochemisuy of zinc enzymes. In Meister A, ed. Advances in enzymology and related areas of molecular biology. New York, Wiley & Sons, 1984, 283 10. Van Houdt K, Nicasi I. Van Mechelen E, VeulemansB, De Ley M: Monoclonal antibodies against metallothioneins from the human liver. Immunol Lett 32:21, 1992
Downloaded from jhc.sagepub.com at UNIV OF NEW ORLEANS on May 29, 2015
