Digital NFATc2 Activation per Cell Transforms Graded T Cell Receptor Activation into an All-or-None IL-2 Expression

Abstract

The expression of interleukin-2 (IL-2) is a key event in T helper (Th) lymphocyte activation, controlling both, the expansion and differentiation of effector Th cells as well as the activation of regulatory T cells. We demonstrate that the strength of TCR stimulation is translated into the frequency of memory Th cells expressing IL-2 but not into the amount of IL-2 per cell. This molecular switch decision for IL-2 expression per cell is located downstream of the cytosolic Ca2+ level. Here we show that in a single activated Th cell, NFATc2 activation is digital but NF-κB activation is graded after graded T cell receptor (TCR) signaling. Subsequently, NFATc2 translocates into the nucleus in an all-or-none fashion per cell, transforming the strength of TCR-stimulation into the number of nuclei positive for NFATc2 and IL-2 transcription. Thus, the described NFATc2 switch regulates the number of Th cells actively participating in an immune response.

Use of immunoglobulins in the prevention of GvHD in a xenogeneic NOD/SCID/γc− mouse model

“…Interestingly, the pattern of cytokine inhibition induced by IVIG was different from one observed with CsA or OKT3. As expected, given their mechanisms of action, 36,[46][47][48][49][50][51][60][61][62] CsA and OKT3 inhibited most cytokines and particularly pro-inflammatory Th1 (IFN-g and IL-2). Of all the cytokines tested, secretion of IFN-g was the highest recorded in PBS-treated mice suggesting that the reduction of GvHD in CSA and OKT3 mice was related to its inhibition.…”

“…Our model also allowed the comparison between IVIG, OKT3 and CsA, an approach that is absolutely impossible in clinical setting for obvious ethical reasons. CsA is a calcineurin inhibitor that inhibits T-cell activation and proliferation 46 by preventing or blocking the synthesis of many cytokines, including IL-2 and IFN-g. [47][48][49][50] OKT3 is a MoAb that directly reacts with the e-chain of the CD3 receptor on the TCR, initiating its clearance from the membrane surface, which leads to the silencing of T-cell allo-reactivity by inducing apoptosis. 36,51 We showed that OKT3 and CsA reduced the incidence of GvHD by up to 60% and also decreased related mortality in NSG mice.…”

“…As expected, we found that after CsA or OKT3 treatment, the number of circulating human CD3 þ cells was reduced in NSG mice. Indeed CsA inhibits T-cell activation and proliferation [46][47][48][49][50] whereas OKT3 induces T-cell apoptosis. 36,51 Unlike OKT3 and CsA, IVIG did not inhibit the proliferation of human T-cells.…”

Polyfunctional responses by human T cells result from sequential release of cytokines

“…These cells exhibited similar asynchronous release of cytokines under persistent stimulation. Variability in the expression levels of kinases, transcription factors, and other signaling proteins (ERK, NFAT, SHP-1) (23,24), along with slow epigenetic events such as chromatin remodeling near transcription factor binding sites that promote production of cytokines (25,26), may contribute to these observed temporal distributions of initial release.…”

Asthma phenotyping, therapy, and prevention: what can we learn from systems biology?

“…Subsequently, a model of differentiation of helper T cells was proposed, describing the expression of, and interactions between, the master regulators (i.e., transcription factors) that determine the phenotypic polarization toward Th1 or Th2 (81). Also, using elegant single-cell measurements and modeling, Podtschaske et al showed that graded T-cell receptor signaling results in graded activation of the transcription factor nuclear factor κB, but a digital activation of transcription factor NFATc2 results in a switch that regulates the number of T lymphocytes actively participating in an immune response (82). In addition, cytokines such as IL-2, which have different effects on different populations of T lymphocytes, have also been studied by combined experimentation and modeling approaches specifically addressing the spatiotemporal complexity (75).…”