Native/citrullinated LL37-specific T-cells help autoantibody production in Systemic Lupus Erythematosus.

LL37 exerts a dual pathogenic role in psoriasis. Bound to self-DNA/RNA, LL37 licenses autoreactivity by stimulating plasmacytoid dendritic cells-(pDCs)-Type I interferon (IFN-I) and acts as autoantigen for pathogenic Th17-cells. In systemic lupus erythematosus (SLE), LL37 also triggers IFN-I in pDCs and is target of pathogenic autoantibodies. However, whether LL37 activates T-cells in SLE and how the latter differ from psoriasis LL37-specific T-cells is unknown. Here we found that 45% SLE patients had circulating T-cells strongly responding to LL37, which correlate with anti-LL37 antibodies/disease activity. In contrast to psoriatic Th17-cells, these LL37-specific SLE T-cells displayed a T-follicular helper-(TFH)-like phenotype, with CXCR5/Bcl-6 and IL-21 expression, implicating a role in stimulation of pathogenic autoantibodies. Accordingly, SLE LL37-specific T-cells promoted B-cell secretion of pathogenic anti-LL37 antibodies in vitro. Importantly, we identified abundant citrullinated LL37 (cit-LL37) in SLE tissues (skin and kidney) and observed very pronounced reactivity of LL37-specific SLE T-cells to cit-LL37, compared to native-LL37, which was much more occasional in psoriasis. Thus, in SLE, we identified LL37-specific T-cells with a distinct functional specialization and antigenic specificity. This suggests that autoantigenic specificity is independent from the nature of the autoantigen, but rather relies on the disease-specific milieu driving T-cell subset polarization and autoantigen modifications.

RelA/NF-kappaB recruitment on the bax gene promoter antagonizes p73-dependent apoptosis in costimulated T cells.

The balance between antiapoptotic and proapoptotic proteins of the Bcl-2 family is critical in determining the fate of T cells in response to death stimuli. Proapoptotic genes, such as bax, are generally regulated by the p53 family of transcription factors, whereas NF-kappaB subunits can activate the transcription of antiapoptotic Bcl-2 members. Here, we show that CD28 activation protects memory T cells from irradiation-induced apoptosis by both upregulating bcl-xL and inhibiting bax gene expression. We found that p73, but not p53, binds to and trans-activates the bax gene promoter in irradiated T cells. The activation of RelA/NF-kappaB subunit in CD28 costimulated T cells and its binding onto the bax gene promoter results in suppression of bax transcription and decrease in both p73 and RNA polymerase II recruitment in vivo. RelA recruitment on the bax gene promoter is also accompanied by the lost of p300 binding and the parallel appearance of histone deacetylase-1-containing complexes. These findings identify RelA/NF-kappaB as a critical regulator of T-cell survival by affecting the balance of Bcl-2 family members.

Mitogen-activated kinase kinase kinase 1 regulates T cell receptor- and CD28-mediated signaling events which lead to NF-kappaB activation.

Optimal activation of Rel/NF-kappaB transcription factors in T lymphocytes requires a CD28-delivered co-stimulatory signal in addition to TCR engagement. Although, Rel/NF-kappaB transcription factors are critical regulators of many T cell functions, the mechanisms and molecules, which link the surface receptors to their activation, are poorly characterized. Using Jurkat T cells stimulated with superantigen presented on B7-positive APC, we showed that CD28- and TCR-stimulated NF-kappaB-dependent transcription is associated to the activation of IkappaB kinase beta (IKKbeta) and, to a lesser extent, of IkappaB kinase alpha (IKKalpha). A dominant negative mutant of the MAP3 kinase MEKK1, a kinase known to regulate the JNK pathway and to activate NF-kappaB-dependent transcription in many cell types, strongly inhibits CD28- and TCR-induced IKK activity, whereas the dominant negative mutants of the NF-kappaB-inducing kinase (NIK) did not exert any significant effects. In addition, TCR/CD28 stimulation results in the recruitment and autophosphorylation of endogenous MEKK1, whereas endogenous NIK was not detectably activated. Our data identify MEKK1 as a critical step in coupling signals initiated by TCR and CD28 to the downstream pathways which lead to both AP-1 and NF-kappaB activation in T lymphocytes.

Peptide analogues as a strategy to induce tolerance in T cells with indirect allospecificity.

BACKGROUND: It has been demonstrated that indirect recognition of allogeneic MHC molecules might play an important role in provoking graft rejection. Although direct recognition of allogeneic molecules on antigen presenting cells of the graft may induce a state of tolerance, the continuous presentation of processed alloantigens by specialized antigen presenting cells does not allow the same phenomenon to occur. Tolerance to interleukin-2 secreting T cells can be achieved in different ways, among these is the exposure to mutants of the wild type allopeptide. We have investigated whether peptide analogues of the allopeptide can induce tolerance in T cells with indirect allospecificity. METHODS: T cell clones with indirect anti-HLA-A2-specificity generated from a HLA-A2-DRB1*1502+ patient who chronically rejected a HLA-A2-expressing kidney allograft were used for this study. Nine peptide analogues of HLA-A2 (residues: 103-120) were produced with single amino acid substitutions at the putative T cell receptor for antigen contact positions. Their effect on the proliferation of a panel of T cell clones was evaluated. RESULTS: Peptide analogues and wild type peptide had similar capacity to bind to the restriction molecule HLA-DRB1*1502. Co-presentation of the peptide analogues 111R/A, H, K and 114H/K, with the wild type peptide inhibited T cell responses, indicative of antagonism. In addition, one analogue 112G/S induced unresponsiveness in the T cells to subsequent culture with the wild type peptide. CONCLUSIONS: The data presented here suggest that using reagents such as altered peptides may represent a strategy to prevent the activation of T cells with indirect alloreactivity and allograft rejection in vivo.

Hypervariable region 1 variants act as TCR antagonists for hepatitis C virus-specific CD4+ T cells.

In various human viral infections, the appearance of mutated epitopes displaying TCR antagonistic activity has been correlated with the severity and persistence of infection. In hepatitis C virus (HCV) infection, where the virus persistence has been associated with the rapid and substantial Ag modifications occurring during replication, TCR antagonism has been evidenced in CD8+ T cell responses. However, CD4+ T cell antagonism may be another important strategy by which HCV eludes a protective response, because sustained Th responses directed against several HCV Ags are associated with a self-limited course of infection. The data reported here represent the first evidence that variants of the hypervariable region (HVR1) of the putative Envelope 2 protein of HCV can act as powerful TCR antagonists for HVR1-specific CD4+ T cells isolated from HCV-infected individuals. Using classical antagonism assays, we observed strong inhibition of cellular proliferation and cytokine production when the agonist and the antagonist ligands were simultaneously presented by the same APCs. The presence in HVR1 of conserved residues, critical for binding to HLA-DR molecules, supports the function of HVR1 variants as TCR antagonists. In conclusion, our data evidence an antagonism phenomenon, which was achieved by naturally occurring class II-restricted T cell epitopes whose mechanism was addressed in terms of the antagonist capacity to inhibit agonist-mediated TCR down-regulation and early signal transduction.

Flipping assumptions and revisioning perioperative services.

As we approach a fully capitated healthcare environment, total revisioning and restructuring of hospitals as a whole, and perioperative services in particular, will be necessary to maintain the financial viability of our healthcare institutions. Nurse executives will be in pivotal roles in leading and influencing these hospital initiatives. The authors present a vision of the new hospital and discuss methods of responding to change within the healthcare environment, with an emphasis on perioperative services. An analysis of the findings of an operating room survey conducted with nurse executives is included in the discussion.