a, Schematic of antibody structures for 4T-Trap, TGF-β-Τrap, anti-CD4 and mGO53. b, Surface plasmon resonance sensorgrams of 4T-Trap and anti-CD4 binding to immobilized CD4 (left) as well as 4T-Trap and anti-TGF-β binding to immobilized TGF-β1 (right). RU, response unit. c, ELISA to assess 4T-Trap, TGF-β-Τrap, anti-CD4 and mGO53 binding to CD4, TGF-β1 or both molecules. Optical density (OD) was detected at 450 nm. d, Inhibition of TGF-β signalling after treatment with the indicated antibodies in HEK293 cells expressing human CD4 (293-hCD4) cells transfected with a TGF-β–SMAD firefly luciferase reporter plasmid (SBE-Luc) and a pRL-TK Renilla luciferase reporter plasmid. RLU, relative unit of normalized firefly luciferase activity to Renilla luciferase activity. e, Flow cytometry analyses of pSMAD2 performed on resting or activated CD4+ T cells from the tumour-draining lymph nodes of mice treated with the indicated antibodies. CD4+ T cells were left untreated (resting) or activated with phorbol acetate and ionomycin for 4 h (activated) before staining for pSMAD2. f, Representative immunofluorescence of CD4 (white) and biotin (red) in the tumour-draining lymph nodes of mice treated with the indicated antibodies. Scale bars, 10 μm. Data are representative of two (b) or three independent experiments (c–f).