Efalizumab modulates T cell function both in vivo and in vitro

G-CSF inhibits LFA-1-mediated CD4+ T cell functions by inhibiting Lck and ZAP-70

In this study, we showed that G-CSF mobilization increased the frequency of T cells, specifically CD3⁺CD4⁺ T cells. G-CSF mobilization decreased the secretion of inflammatory cytokines of CD4⁺ T cells through the LFA-1/ICAM-1 signaling pathway, whereas it did not alter the TH1/TH2 ratio. We found that G-CSF mobilization inhibited LFA-1-mediated CD4⁺ T cell polarization and motility. In vitro, G-CSF stimulation also attenuated the polarization and adhesiveness of CD4⁺ T cells through the LFA-1/ICAM-1 interaction. Further investigation revealed that G-CSF mobilization suppressed LFA-1 signaling by down-regulating Lck and ZAP-70 expression in CD4⁺ T cells, similar results was also confirmed by in-vitro studies. These findings suggested that G-CSF directly suppressed LFA-1-mediated CD4⁺ T cell functions through the down-regulation of Lck and ZAP-70. The immunosuppressive effect of G-CSF mobilization deepened our understanding about peripheral blood hematopoietic stem cell transplantation. LFA-1/ICMA-1 pathway may become a potential target for graft-versus-host disease prophylaxis.

Immunosuppression strategies in liver transplantation patient; patients with hepatocellular carcinoma

Hepatocellular carcinoma (HCC) consists the main primary malignant tumor of the liver. There is an underlining liver cirrhosis mainly attributed to chronic hepatitis B virus or hepatitis C virus, alcoholic liver disease, nonalcoholic steatohepatitis and other pathologic conditions. Liver transplantation consists a radical management, treating both cancer and cirrhosis. By introducing the Milan Criteria for liver transplantation in HCC patients there was a 5-year survival escalation. Even though there is a careful selection of patients with HCC for transplantation, recurrent disease is still high. The role of immusuppression therapy is of paramount importance, in order to avoid acute and chronic graft rejection while protecting the patient from tumor recurrence. In recent years newer immunosuppressive agents such as the mTOR inhibitors are proposed, having dual properties, as both immunosuppressive and antitumors agents.

Downstream effect profiles discern different mechanisms of integrin αLβ2 inhibition

The integrin leucocyte function-associated antigen-1 (αLβ2, LFA-1) plays crucial roles in T cell adhesion, migration and immunological synapse (IS) formation. Consequently, αLβ2 is an important therapeutic target in autoimmunity. Three major classes of αLβ2 inhibitors with distinct modes of action have been described to date: Monoclonal antibodies (mAbs), small molecule α/β I allosteric and small molecule α I allosteric inhibitors. The objective of this study was to systematically compare these three modes of αLβ2 inhibition for their αLβ2 inhibitory as well as their potential agonist-like effects. All inhibitors assessed were found to potently block αLβ2-mediated leucocyte adhesion. None of the inhibitors induced ZAP70 phosphorylation, indicating absence of agonistic outside-in signalling. Paradoxically, however, the α/β I allosteric inhibitor XVA143 induced conformational changes within αLβ2 characteristic for an intermediate affinity state. This effect was not observed with the α I allosteric inhibitor LFA878 or the anti-αLβ2 mAb efalizumab. On the other hand, efalizumab triggered the unscheduled internalization of αLβ2 in CD4+ and CD8+ T cells while LFA878 and XVA143 did not affect or only mildly reduced αLβ2 surface expression, respectively. Moreover, efalizumab, in contrast to the small molecule inhibitors, disturbed the fine-tuned internalization/recycling of engaged TCR/CD3, concomitantly decreasing ZAP70 expression levels. In conclusion, different modes of αLβ2 inhibition are associated with fundamentally different biologic effect profiles. The differential established here is expected to provide important translational guidance as novel αLβ2 inhibitors will be advanced from bench to bedside.

Mechanisms of LtxA (Leukotoxin), a Potent New Anti-Inflammatory Agent for the Treatment of Alopecia Areata

Alopecia areata is an autoimmune condition where activated, pro-inflammatory white blood cells (WBCs) attack the hair follicles, resulting in hair loss. Migration of these activated WBCs from the blood stream and into the follicle tissue requires interaction between the integrin, lymphocyte function-associated antigen-1 (LFA-1) on WBCs, and ICAM-1 on vascular endothelial cells. High levels of active LFA-1 are uniquely expressed on WBCs that are involved in autoimmune and inflammatory conditions. The natural biologic agent LtxA (Leukothera) preferentially targets and depletes disease activated and malignant WBCs by binding to active LFA-1. The experimental drug has demonstrated significant therapeutic efficacy against autoimmune/inflammatory conditions such as psoriasis and allergic asthma in mouse models for these diseases. In addition, when injected into rodents, rhesus macaques, and dogs, LtxA was demonstrated to be physiologically active, biologically specific, and extremely well-tolerated. LFA-1 is an attractive target for therapy because it is only normally present on WBCs and has been shown to be activated and overexpressed on WBCs that are responsible for autoimmune/inflammatory conditions.

Precision Subtypes of T Cell-Mediated Rejection Identified by Molecular Profiles

Among kidney transplant recipients, the treatment of choice for acute T cell-mediated rejection (TCMR) with pulse steroids or antibody protocols has variable outcomes. Some rejection episodes are resistant to an initial steroid pulse, but respond to subsequent antibody protocols. The biological mechanisms causing the different therapeutic responses are not currently understood. Histological examination of the renal allograft is considered the gold standard in the diagnosis of acute rejection. The Banff Classification System was established to standardize the histopathological diagnosis and to direct therapy. Although widely used, it shows variability among pathologists and lacks criteria to guide precision individualized therapy. The analysis of the transcriptome in allograft biopsies, which we analyzed in this study, provides a strategy to develop molecular diagnoses that would have increased diagnostic precision and assist the development of individualized treatment. Our hypothesis is that the histological classification of TCMR contains multiple subtypes of rejection. Using R language algorithms to determine statistical significance, multidimensional scaling, and hierarchical, we analyzed differential gene expression based on microarray data from biopsies classified as TCMR. Next, we identified KEGG functions, protein–protein interaction networks, gene regulatory networks, and predicted therapeutic targets using the integrated database ConsesnsusPathDB (CPDB). Based on our analysis, two distinct clusters of biopsies termed TCMR01 and TCMR02 were identified. Despite having the same Banff classification, we identified 1933 differentially expressed genes between the two clusters. These genes were further divided into three major groups: a core group contained within both the TCMR01 and TCMR02 subtypes, as well as genes unique to TCMR01 or TCMR02. The subtypes of TCMR utilized different biological pathways, different regulatory networks and were predicted to respond to different therapeutic agents. Our results suggest approaches to identify more precise molecular diagnoses of TCMR, which could form the basis for personalized treatments.

Leukocyte function-associated antigen-1/intercellular adhesion molecule-1 interaction induces a novel genetic signature resulting in T-cells refractory to transforming growth factor-β signaling

The immunesuppressive cytokine TGF-β plays crucial regulatory roles in the induction and maintenance of immunologic tolerance and prevention of immunopathologies. However, it remains unclear how circulating T-cells can escape from the quiescent state maintained by TGF-β. Here, we report that the T-cell integrin leukocyte function-associated antigen-1 (LFA-1) interaction with its ligand intercellular adhesion molecule-1 (ICAM-1) induces a genetic signature associated with reduced TGF-β responsiveness via up-regulation of SKI, E3 ubiquitin-protein ligase SMURF2, and SMAD7 (mothers against decapentaplegic homolog 7) genes and proteins. We confirmed that the expression of these TGF-β inhibitory molecules was dependent on STAT3 and/or JNK activation. Increased expression of SMAD7 and SMURF2 in LFA-1/ICAM-1 cross-linked T-cells resulted in impaired TGF-β-mediated phosphorylation of SMAD2 and suppression of IL-2 secretion. Expression of SKI caused resistance to TGF-β-mediated suppression of IL-2, but SMAD2 phosphorylation was unaffected. Blocking LFA-1 by neutralizing antibody or specific knockdown of TGF-β inhibitory molecules by siRNA substantially restored LFA-1/ICAM-1-mediated alteration in TGF-β signaling. LFA-1/ICAM-1-stimulated human and mouse T-cells were refractory to TGF-β-mediated induction of FOXP3(+) (forkhead box P3) and RORγt(+) (retinoic acid-related orphan nuclear receptor γt) Th17 differentiation. These mechanistic data suggest an important role for LFA-1/ICAM-1 interactions in immunoregulation concurrent with lymphocyte migration that may have implications at the level of local inflammatory response and for anti-LFA-1-based therapies.