In vivo anergized CD4+ T cells express perturbed AP-1 and NF-kappa B transcription factors.

Abstract

Anergy is a major mechanism to ensure antigen-specific tolerance in T lymphocytes in the adult. In vivo, anergy has mainly been studied at the cellular level. In this study, we used the T-cell-activating superantigen staphylococcal enterotoxin A (SEA) to investigate molecular mechanisms of -T-lymphocyte anergy in vivo. Injection of SEA to adult mice activates CD4+ T cells expressing certain T-cell receptor (TCR) variable region a8-chain families and induces strong and rapid production of interleukin 2 (IL-2). In contrast, repeated injections of SEA cause CD4+ T-cell deletion and anergy in the remaining CD4+ T cells, characterized by reduced expression of IL-2 at mRNA and protein levels. We analyzed expression of AP-1, NF-KcB, NF-AT, and octamer binding transcription factors, which are known to be involved in the regulation of IL-2 gene promoter activity. Large amounts of AP-1 and NF-cB and significant quantities of NF-AT were induced in SEA-activated CD4+ spleen T cells, whereas Oct-1 and Oct-2 DNA binding activity was similar in both resting and activated T cells. In contrast, anergic CD4+ T cells contained severely reduced levels ofAP-1 and Fos/Juncontaining NF-AT complexes but expressed significant amounts of NF-KcB and Oct binding proteins after SEA stimulation. Resolution of the NF-cB complex demonstrated predominant expression of p50-p65 heterodimers in activated CD4+ T cells, while anergic cells mainly expressed the transcriptionally inactive p50 homodimer. These alterations of transcription factors are likely to be responsible for repression of IL-2 in anergic T cells.Staphylococcal enterotoxins (SEs) belong to a family of bacterial proteins denoted as superantigens (SAgs) because of their ability to activate a high frequency of both CD4+ and CD8+ T cells expressing certain T-cell receptor (TCR) variable region f3 chains (Vp) (1,2). Administration of SE to adult mice induces rapid production of a panel of cytokines, including interleukin 2 (IL-2) and tumor necrosis factor (TNF), and subsequent expansion of reactive T-cell populations (3). After the initial phase of SE-induced activation in vivo, part of the reactive CD4+ T cells are deleted and the remaining CD4+ T-cell population fails to proliferate and secrete IL-2 in response to a subsequent SE challenge (4).

Myotrophin/V-1, a Protein Up-regulated in the Failing Human Heart and in Postnatal Cerebellum, Converts NFκB p50-p65 Heterodimers to p50-p50 and p65-p65 Homodimers

“…For example, during B lymphocyte cell differentiation (40 -42), dynamic exchange of NF B subunits are known to occur among the activated NF B dimers resulting in altered gene expression appropriate for the stage of differentiation. During endotoxin tolerance in monocytes (73), T-lymphocyte anergy (74), and chronic TNF exposure to mouse myocardium (75), the levels of p50-p50 homodimers are known to increase during late stages of these events, suggesting a dynamic qualitative and quantitative change in the activated NF B dimers. Moreover, In human sepsis, large amounts of p50-p50 homodimers exceeding the levels of p50-p65 heterodimers were observed in monocytes of non-survivors compared with the survivors, further suggesting an important role for NF B dimer ratio in the pathophysiology of sepsis (76).…”

“…9A) to shift the NF B dimer ratio from transcriptionally active heterodimers to transcriptionally repressive homodimers is also highly significant. In fact, in many biological scenarios like B lymphocyte cell differentiation (40 -42), lipopolysaccharide tolerance (73), T-lymphocyte anergy (74), and chronic TNF exposure to mouse myocardium (75), the activated NF B dimers are known to change both quantitatively and qualitatively during these events. For example, during B lymphocyte cell differentiation (40 -42), dynamic exchange of NF B subunits are known to occur among the activated NF B dimers resulting in altered gene expression appropriate for the stage of differentiation.…”

Bcl-3 and NFκB p50-p50 Homodimers Act as Transcriptional Repressors in Tolerant CD4+ T Cells

“…AP-1, NFAT, and NF B families of transcription factors are essential in T cell activation as coordinators of IL-2 transcription (9) and tolerant CD4 ϩ T cell clones as well as in vivo tolerized T cells possess reduced AP-1 binding to the IL-2 promoter (10 -12). In addition, we have previously shown that CD4 ϩ T cells from mice tolerized in vivo express qualitative alterations in the composition of the NF B complex (13). Defective NF B expression is also a feature of tolerant B cells (14,15).…”

Cutting Edge: Cell Autonomous Rather Than Environmental Factors Control Bacterial Superantigen-Induced T Cell Anergy In Vivo

“…On the one hand, several studies described molecular alterations in TCR signaling in anergic cells. In vivo SE-anergized T cells exhibited impaired protein phosphorylation (8) and defective expression of the AP-1 and NF-B transcription factors (9,10). In addition, anergic cells displayed altered signaling via the common ␥-chain of the IL-2 receptor, which consequently resulted in diminished phosphorylation of several downstream proteins (11).…”