Induction of latency‐associated peptide (transforming growth factor‐β 1 ) expression on CD4 + T cells reduces Toll‐like receptor 4 ligand‐induced tumour necrosis factor‐α production in a transforming growth factor‐β‐dependent manner

Summary CD4 + T cells expressing the latent form of transforming growth factor‐β [latency‐associated peptide (LAP) (TGF‐β 1 )] play an important role in the modulation of immune responses. Here, we identified a novel peptide ligand (GPC 81–95 ) with an intrinsic ability to induce membrane‐bound LAP (TGF‐β 1 ) expression on a subpopulation of human CD4 + T cells (using flow cytometry; ranging from 0·8% to 2·6%) and stimulate peripheral blood mononuclear cells to release LAP (TGF‐β 1 ) (using ELISPOT assay; ranging from 0·03% to 0·16%). In spite of this low percentage of responding cells, GPC 81–95 significantly reduced Toll‐like receptor 4 ligand‐induced tumour necrosis factor‐α production in a TGF‐β 1 ‐ and CD4 + T‐cell‐dependent manner. The results demonstrate that GPC 81–95 is a useful tool to study the functional properties of a subpopulation of LAP (TGF‐β 1 ) +  CD4 + T cells and suggest a pathway that can be exploited to suppress inflammatory response.