T cell activation in health and diseases

Field of Interest

Figure 1. Current view of TAMs and MDSCs differentiation. HSCs give rise to common myeloid precursors (CMPs), which subsequently originate at least three subsets of cells circulating in tumor-bearing hosts that can be identified by specific markers: monocytes (CD11b⁺Gr-1⁺F4/80⁺), granulocytes (CD11b⁺Gr-1^highF4/80^-IL-4Rα^-), and MDSCs (CD11b⁺Gr-1^medF4/80^low/-IL-4Rα⁺). Circulating monocytes are recruited by tumors and differentiate into TAMs, acquiring protumoral functions. During tumor progression, MDSCs accumulating in blood and in lymphoid organs such as the spleen may also be recruited to the tumor microenvironment, where they become F4/80⁺. This latter pathway of MDSC-TAM phenotype transition (dashed arrow) was recently proposed Finally, it has been hypothesized that immature forms of granulocytes might differentiate into MDSCs or condition their function and/or further differentiation (red arrows). J Clin Invest. 2007, 117:1155-1166.

Figure 1. Current view of TAMs and MDSCs differentiation. HSCs give rise to common myeloid precursors (CMPs), which subsequently originate at least three subsets of cells circulating in tumor-bearing hosts that can be identified by specific markers: monocytes (CD11b⁺Gr-1⁺F4/80⁺), granulocytes (CD11b⁺Gr-1^highF4/80^-IL-4Rα^-), and MDSCs (CD11b⁺Gr-1^medF4/80^low/-IL-4Rα⁺). Circulating monocytes are recruited by tumors and differentiate into TAMs, acquiring protumoral functions. During tumor progression, MDSCs accumulating in blood and in lymphoid organs such as the spleen may also be recruited to the tumor microenvironment, where they become F4/80⁺. This latter pathway of MDSC-TAM phenotype transition (dashed arrow) was recently proposed Finally, it has been hypothesized that immature forms of granulocytes might differentiate into MDSCs or condition their function and/or further differentiation (red arrows). J Clin Invest. 2007, 117:1155-1166.
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Tumor-induced T cell tolerance is a major mechanism that facilitates tumor progression and limits the efficacy of immune-based therapeutic interventions. My group is focused on the characterization of myeloid derived suppressor cells (MDSCs), one of the cell type recruited by tumors to impair T cell function. Within the past few years, my group contributed to demonstrate the role of MDSCs as potent suppressor of the antitumor immune responses, both in the tumor microenvironment and lymphoid organs. We found that it was possible to rouse lymphocytes and induce cancer cell killing by interfering with the activity of two enzymes, arginase and nitric oxide synthase, highly expressed in MDSCs.
Based on our previous findings, we are currently trying to address different issues related to MDSC biology:

1. Molecular mechanisms regulating the recruitment and differentiation of MDSCs to the tumor-conditioned environment. With a cocktail of different cytokines, we are able to derive MDSCs in vitro starting from bone marrow (BM) precursor cells; these myeloid cells are equal in phenotype and suppressive activity to MDCSs elicited by tumors. We are dissecting the relationship among tumor-released cytokines, intracellular signalling, microRNAs, and transcription factors that sustain this differentiation process.
2. Use of in vitro-derived MDSCs for the treatment of autoimmune diseases and transplant rejection. We are currently evaluating the therapeutic effect of bone marrow (BM)-derived MDSCs in a setting of allogeneic pancreatic insulae transplantation in pharmacologically-induced diabetic mice. Adoptive transfer of recipient BM-MDSCs increases the percentage of long term survivors in the group of mice transplanted with allogenic insulae, indicating that in vitro generated MDSCs might represent a novel, drug-free approach to provide transient immunosuppression and graft tolerance.
3. It is quite well established that MDCSs are able to induce immunosuppression acting directly on CD8⁺ T cells but also indirectly, by supporting proliferation of antigen-specific, naturally occurring T regulatory cells. With the use of novel conditional knock out and transgenic mice, we are exploring the intervention of arginine metabolizing enzymes in these two processes.
4. Drugs controlling the enzymes arginase and nitric oxide synthase might be useful to aid immunotherapeutic approaches for the treatment of cancer, by creating a favorable tumor environment for lymphocyte activation. Thus, we have designed and developed novel small molecules aimed at interfering in vivo with arginase and nitric oxide synthase metabolic pathways.

Synoptic CV

Honours

Selected Publications (VIMM)

Additional Publications

Selected Seminars

Contact

Vincenzo Bronte Venetian Institute of Molecular Medicine Via Orus 2 35129 Padua — Italy

Tel.:  (+39) 049 7923 228 Fax:  (+39) 049 7923 260

Last updated: March 2007, VB ·

T cell activation in health and diseases

Field of Interest

Figure 1.The actin-binding protein FLNa is required for CD28-induced raft organization and recruitment into the immunological synapse. Jurkat T cells expressing the raft marker MyrPalm-mCFP (in red in the figure) were transfected (B) or not (A) with Myc-tagged FLNaD10-12, a FLNa fragment that functions as a dominant-negative mutant which prevents CD28 interaction with endogenous FLNa. In this figure, two confocal images of fixed conjugates (between Jurkat cells and SEE-pulsed 5-3.1/B7 antigen presenting cells) with raft recruitment into the immunological synapse in the presence of wt FLNa (A) and loss of the recruitment when the FLNaD10-12 mutant is expressed (B). Scale bars, 10 µm.

Figure 1.The actin-binding protein FLNa is required for CD28-induced raft organization and recruitment into the immunological synapse. Jurkat T cells expressing the raft marker MyrPalm-mCFP (in red in the figure) were transfected (B) or not (A) with Myc-tagged FLNaD10-12, a FLNa fragment that functions as a dominant-negative mutant which prevents CD28 interaction with endogenous FLNa. In this figure, two confocal images of fixed conjugates (between Jurkat cells and SEE-pulsed 5-3.1/B7 antigen presenting cells) with raft recruitment into the immunological synapse in the presence of wt FLNa (A) and loss of the recruitment when the FLNaD10-12 mutant is expressed (B). Scale bars, 10 µm.
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My group studies signals modulating the immune response in physiopathological conditions. We try understanding how to help lymphocytes to fight cancer or viruses on the one side, and, on the other, how to block improper lymphocyte activation and thus autoimmune diseases.

Throughout its life, a naïve T lymphocyte continually circulates between blood and lymph nodes searching for the right partner, an antigen-presenting cell (APC) carrying peptide-MHC complexes specific for its antigen-recognition receptors. After this encounter occurring in a specialized area of the lymph nodes, T cells migrate into the inflamed tissue and exert their effector functions. We can therefore identify three distinct phases in T lymphocyte physiology: 1) T cell migration; 2) T cell priming; 3) T cell migration and effector functions.

Figure 2. Mitochondria fission is required for recruitment of the organelles to the cell uropod, phenomenon that constrains lymphocyte polarization and migration. Jurkat T cells were co-transfected with mtRFP and empty vector (A-C), mtRFP and the pro-fission protein DRP1 (D-F), or mtRFP and the pro-fusion protein OPA1 (G-I). Confocal images of mitochondrial shape in resting (A, B, D, E, G, H) or polarized cells (C, F, I). (A, D, G) Volume-rendered 3D reconstructions of mitochondrial network. When transfected with DRP1 the cells showed fragmented mitochondria (E) and, after chemokine treatment, a polarized phenotype (F). In contrast, when OPA1 was overexpressed, the cells showed fused mitochondria (H), and the impaired polarization in response to chemokine, as shown in (I). Scale bar, 5 µm.

Figure 2. Mitochondria fission is required for recruitment of the organelles to the cell uropod, phenomenon that constrains lymphocyte polarization and migration. Jurkat T cells were co-transfected with mtRFP and empty vector (A-C), mtRFP and the pro-fission protein DRP1 (D-F), or mtRFP and the pro-fusion protein OPA1 (G-I). Confocal images of mitochondrial shape in resting (A, B, D, E, G, H) or polarized cells (C, F, I). (A, D, G) Volume-rendered 3D reconstructions of mitochondrial network. When transfected with DRP1 the cells showed fragmented mitochondria (E) and, after chemokine treatment, a polarized phenotype (F). In contrast, when OPA1 was overexpressed, the cells showed fused mitochondria (H), and the impaired polarization in response to chemokine, as shown in (I). Scale bar, 5 µm.
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1) Cell migration

We have recently demonstrated that leukocyte migration is controlled by mitochondrial shape and position inside the cells. We found that during leukocyte migration mitochondria specifically concentrate at the uropod by a process involving rearrangements of their shape and suggested that mitochondria redistribution is required to fuel the motor of migrating cells.

2) T cell priming

We study the interaction between T cells and APCs. In particular, we analyze the role of plasma membrane lipid microdomain — known as "lipid rafts" — and chemokine receptors at the immunological synapse.

3) T cell effector functions

Prostate cancer is the second leading cause of malignancy-related mortality in males in the Western world and available treatments for its metastatic form have demonstrated weak curative efficacy. It is therefore necessary to find alternative therapeutic approaches prostate cancer and immunotherapy may represent an interesting possibility. To analyze the modulation of T cell responses by the prostate tumor environment, we performed a study based on the use of collagen gel-matrix supported organ cultures of human prostate carcinomas. Our results identified a novel and dominant mechanism by which cancers induce immunosuppression in situ and suggest novel strategies for tumor immunotherapy.

Synoptic CV

Honours

Selected Publications (VIMM)

Additional Publications

Selected Seminars

Contact

Antonella Viola Venetian Institute of Molecular Medicine Via Orus 2 35129 Padua — Italy

Tel. lab.:  (+39) 049 7923 230 Fax:  (+39) 049 7923 260

Last updated: March 2007, AV ·