Connective tissue growth factor does not affect transforming growth factor-beta 1-induced Smad3 phosphorylation and T lymphocyte proliferation inhibition

Transforming growth factor-beta 1 (TGF-beta(1)) is a key regulator of immune tolerance. TGF-beta(1) controls T lymphocte activation and is involved in the immunosuppressive function and generation of regulatory T lymphocytes. Connective tissue growth factor (CTGF) has an essential role in the formation of connective tissue and blood vessels. CTGF expression is induced by TGF-beta(1) in several cell types and CTGF mediates several of the downstream actions of TGF-beta(1). Since little is known about the potential synergy between CTGF and TGF-beta(1) in T lymphocyte biology, the purpose of the present study was to determine whether CTGF can modulate TGF-beta(1)-mediated effects on human CD4+ T lymphocytes. Human recombinant CTGF was expressed in HEK293 cells. rCTGF was biologically active demonstrated by induction of proliferation in the endothelial cell line EA hy 926. rCTGF alone did not potentiate or diminish anti-CD3-induced CD4+ T lymphocyte proliferation and did not activate the Smad signaling pathway in CD4+ T lymphocytes. Furthermore, rCTGF did not attenuate TGF-beta(1)-mediated inhibition of CD4+ T lymphocyte proliferation and TGF-beta(1)-induced Smad signaling in CD4+ T lymphocytes. These results indicate that rCTGF had no detectable effects of its own on human CD4+ T lymphocytes and did not potentiate the effects of low amounts of TGF-beta(1) on human CD4+ T lymphocytes. Overall, these data support the hypothesis that CTGF does not act on CD4+ T lymphocytes. Copyright (c) 2008 S. Karger AG, Basel.