科研之友
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摘要
Background: It is generally assumed that T cells do not produce active TGF-beta since active TGF-beta as measured in supernatants by ELISA without acidification is usually not detectable. However, it is possible that active TGF-beta from T cells may take a special form which is not detectable by ELISA. Methodology/Principal Findings: We constructed a TGF-beta bioassay which can detect both soluble and membrane-bound forms of TGF-beta from T cells. For this bioassay, 293T cells were transduced with (caga)(12) Smad binding element-luciferase along with CD32 (Fc receptor) and CD86. The resulting cells act as artificial antigen presenting cells in the presence of anti-CD3 and produce luciferase in response to biologically active TGF-beta. We co-cultured pre-activated murine CD4(+)CD25(-) T cells or CD4(+)CD25(+) T cells with the 293T-caga-Luc-CD32-CD86 reporter cells in the presence of anti-CD3 and IL-2. CD4(+)CD25(-) T cells induced higher luciferase in the reporter cells than CD4(+)CD25(+) T cells. This T cell-produced TGF-b is in a soluble form since T cell culture supernatants contained the TGF-beta activity. The TGF-beta activity was neutralized with an anti-mouse LAP mAb or an anti-latent TGF-beta/pro-TGF-beta mAb, but not with anti-active TGF-beta Abs. An anti-mouse LAP mAb removed virtually all acid activatable latent TGF-beta from the T cell culture supernatant, but not the ability to induce TGF-beta signaling in the reporter cells. The induction of TGF-beta signaling by T cell culture supernatants was cell type-specific. Conclusions/Significance: A newly developed 293T-caga-Luc-CD32-CD86 reporter cell bioassay demonstrated that murine CD4 T cells produce an unconventional form of TGF-beta which can induce TGF-beta signaling. This new form of TGF-beta contains LAP as a component. Our finding of a new form of T cell-produced TGF-beta and the newly developed TGF-beta bioassay system will provide a new avenue to investigate T cell function of the immune system.
- 出版日期2011-4-11
