TGF- β is a highly pleiotropic cytokine and a well-known suppressor of inflammatory T cells. Dysregulation in TGF- β function is associated with multiple pathological phenomenons including tumor cell growth, fibrosis and autoimmunity. GARP (glycoprotein A repetitions predominant) is an activation maker on human regulatory T cells (Treg) which is known to modulate the bioavailability of TGF- β . To address the cell-independent regulatory capacity of GARP we generated a soluble GARP protein (sGARP). Interestingly, T cells cultured in presence of sGARP showed SMAD2/3 phosphorylation similar to TGF- β treated T cells. In addition, sGARP function was inhibited by blockade of TGF- β -signaling, s…

GARP inhibits allergic airway inflammation in a humanized mouse model

Background Regulatory T cells (Treg) represent a promising target for novel treatment strategies in patients with inflammatory/allergic diseases. A soluble derivate of the Treg surface molecule glycoprotein A repetitions predominant (sGARP) has strong anti-inflammatory and regulatory effects on human cells in vitro as well as in vivo through de novo induction of peripheral Treg. The aim of this study was to investigate the immunomodulatory function of sGARP and its possible role as a new therapeutic option in allergic diseases using a humanized mouse model. Methods To analyze the therapeutic effects of sGARP, adult NOD/Scidγc−/− (NSG) mice received peripheral blood mononuclear cells (PBMC) …

Soluble GARP has potent antiinflammatory and immunomodulatory impact on human CD4+ T cells

Glycoprotein A repetitions predominant (GARP) is expressed on the surface of activated human regulatory T cells (Treg) and regulates the bioavailability of transforming growth factor-β (TGF-β). GARP has been assumed to require membrane anchoring. To investigate the function of GARP in more detail, we generated a soluble GARP protein (sGARP) and analyzed its impact on differentiation and activation of human CD4⁺ T cells. We demonstrate that sGARP efficiently represses proliferation and differentiation of naïve CD4⁺ T cells into T effector cells. Exposure to sGARP induces Foxp3, decreases proliferation and represses interleukin (IL)-2 and interferon-γ production, resulting in differentiation …