Mucosae-associated epithelial chemokine (MEC) is a novel chemokine whose mRNA is most abundant in salivary gland, with strong expression in other mucosal sites, including colon, trachea, and mammary gland. MEC is constitutively expressed by epithelial cells; MEC mRNA is detected in cultured bronchial and mammary gland epithelial cell lines and in epithelia isolated from salivary gland and colon using laser capture microdissection, but not in the endothelial, hemolymphoid, or fibroblastic cell lines tested. Although MEC is poorly expressed in skin, its closest homologue is the keratinocyte-expressed cutaneous T cell-attracting chemokine (CTACK; CCL27), and MEC supports chemotaxis of transfected lymphoid cells expressing CCR10, a known CTACK receptor. In contrast to CTACK, however, MEC also supports migration through CCR3. Consistent with this, MEC attracts eosinophils in addition to memory lymphocyte subsets. These results suggest an important role for MEC in the physiology of extracutaneous epithelial tissues, including diverse mucosal organs.
Integrin receptors are important for regulating lymphocyte recirculation and recruitment to sites of inflammation. Transfectants of the B cell lymphoma 38C13 were generated that differ exclusively in the expression of integrin beta 1 or beta 7 subunits allowing for a functional comparison of lymphocyte Peyer's patch HEV adhesion molecule 1 (LPAM-1) (alpha 4 beta 7) and very late antigen 4 (VLA-4) (alpha 4 beta 1) in an identical cellular environment. Whereas 38-beta 7 transfectants bound to purified and cellular mucosal addressin cell adhesion molecule (MAdCAM-1), unstimulated 38-beta 1 cells failed to bind MAdCAM-1. Treatment of 38-beta 1 cells with Mn2+ but not with PMA induced low level binding to MAdCAM-1. MAdCAM-1 adhesion of 38-beta 7 cells was constitutive and not enhanced by Mn2+ treatment. Similarly, MAdCAM-1-dependent adhesion to mucosal high endothelial venules was shown for 38-beta 7 but not for 38-beta 1 cells. The results therefore establish the LPAM-1-MAdCAM-1 interaction as the functionally dominant adhesion pathway for regulating lymphocyte homing to mucosal sites. Nonetheless, the activated VLA-4 on some lymphocytes may be involved in MAdCAM-1 recognition or promote binding to MAdCAM-1 in other tissues. By contrast, 38-beta 7 and 38-beta 1 transfectants did not differ in their binding capacity for vascular cell adhesion molecule 1 (VCAM-1) or fibronectin and LPAM-1 did not display any preference for interacting with either MAdCAM-1 or VCAM-1. LPAM-1 may therefore contribute significantly to cellular functions previously attributed to VLA-4. Interestingly, functional analysis of the intraepithelial lymphocyte integrin alpha IEL beta 7 which is structurally related to LPAM-1 did not reveal detectable binding activity for MAdCAM-1, VCAM-1, or fibronectin.
To analyze the role of a4-integrins in lymphoma metastasis, sublines of the T-cell lymphoma LB were generated by retrovirus-mediated gene transfer that differ exclusively in the expression of a4-integrins. Using LB-a4 and control LB-NTK cells, we demonstrate that expression of a4-integrins strongly suppresses metastasis formation of LB lymphoma cells in secondary lymphoid organs (15)(16)(17)20).In the present study, the role of a4-integrins in lymphoma metastasis was studied by using the murine T-cell lymphoma LB as a model. We demonstrate that expression of a4-integrins strongly reduces metastasis formation by LB cells after i.v. injection. On the basis of the route of injection, in vivo migration experiments, and analysis of intrinsic growth rates, we conclude that metastasis formation of disseminated lymphoma cells is inhibited at a stage subsequent to infiltration of target organs. MATERIALS AND METHODSCells and Antibodies. Antibodies used included rat antimurine integrin a4, PS/2 (American Type Culture Collection); rat anti-murine LFA-1 a chain, FD441.8 (American Type Culture Collection); rat anti-murine integrin ,B7, Fib3O and Fib 504 (21); rat anti-murine integrin aE, M290 (22); rat antimurine integrin a5, 5H10-27 (PharMingen); rat anti-murine integrin a6, EA-1 (23); rat anti-murine L-selectin, MEL-14 (American Type Culture Collection); rat anti-murine CD44, IM781 (24); and rat anti-murine T-cell receptor Vf37, TR310 as negative control (25). For flow cytometry analysis, cells were incubated with saturating amounts of mAbs, washed, and stained with fluorescein isothiocyanate-conjugated mouse F(ab)2 fragments reacting with rat Ig (Dianova, Hamburg, Germany) and analyzed on a Coulter EPICS XL cytometer.The T-cell lymphoma LB spontaneously developed in a BALB/c mouse (26). LB cells express cell surface CD8 and CD25 but are negative for CD3 and CD4 (26).Generation of LB-a4 and LB-NTK Cell Lines. Expression plasmid pNTK-a4 was constructed by cloning the murine a4 cDNA (27) into the retroviral vector pNTK (28). Recombinant retroviruses were prepared from the mouse ecotropic, helper virus-free producer line . LB cells were infectedAbbreviations: VCAM-1, vascular cell adhesion molecule 1; MAd-CAM-1, mucosal addressin cell adhesion molecule 1. 4821The publication costs of this article were defrayed in part by page charge payment. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. §1734 solely to indicate this fact.
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