The murine homolog of human Ep-CAM, a homotypic adhesion molecule, is expressed by thymocytes and thymic epithelial cells.
In this report, we demonstrate that gp40, a molecule previously shown to be expressed by thymic epithelial cell lines in vitro and by thymic epithelial cells in vivo, is the murine homolog of human Ep-CAM, a calcium-independent homotypic adhesion molecule. gp40 is also expressed at low levels by thymocytes and peripheral T cells. In the adult thymus, gp40 expression was inversely related to the state of thymocyte maturation, with the highest levels associated with CD4-CD8- and CD4+CD8+ thymocyte populations. Ultrastructural immunohistochemistry revealed gp40 localization to areas of thymocyte/epithelial contact and demonstrated that gp40 is also expressed by thymic dendritic cells. During fetal development, thymocytes at days 14-16 of gestation expressed high levels of gp40. At later stages, the observed decline in the frequency of gp40+ cells and levels of expression correlated with the emergence of alpha beta+ thymocytes by day 18 of gestation. In short-term cultures, stimulation of unfractionated adult thymocytes with concanavalin A increased gp40 expression, particularly among CD3hi and CD3int thymocyte populations. This demonstration that Ep-CAM, initially considered to be expressed primarily by epithelial cells, is also expressed by thymocytes, T cells and antigen-presenting cells, raises the possibility that Ep-CAM may contribute to adhesive interactions between thymocytes and epithelial cells or dendritic cells, either in the context of thymocyte development or peripheral T cell trafficking and function.
Nelson
A J
AJ
Department of Biological Structure, University of Washington, Seattle 98196-7420, USA.
Dunn
R J
RJ
Peach
R
R
Aruffo
A
A
Farr
A G
AG
D000818:Animals; D000911:Antibodies, Monoclonal / Q000737:chemistry; D000951:Antigens, Neoplasm / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D015815:Cell Adhesion Molecules / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D002454:Cell Differentiation / Q000276:immunology; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000378:metabolism; D000071858:Epithelial Cell Adhesion Molecule; D004848:Epithelium / Q000378:metabolism; D005260:Female; D006801:Humans; D008213:Lymphocyte Activation; D051379:Mice; D008807:Mice, Inbred BALB C; D008934:Mitogens / Q000494:pharmacology; D008970:Molecular Weight; D013601:T-Lymphocytes / Q000145:classification / Q000378:metabolism*; D013950:Thymus Gland / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D015854:Up-Regulation
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; D000071858:Epithelial Cell Adhesion Molecule; D008934:Mitogens