Regulatory T-cell development and function are impaired in mice lacking membrane expression of full length intercellular adhesion molecule-1.

To further investigate the contribution of intercellular adhesion molecule-1 (ICAM-1) to adaptive immune responses, we analysed T-cell development and function in mice lacking full-length ICAM-1 (ICAM-1(tm1Jcgr) ). Compared with wild-type (ICAM-1(WT) ) mice, ICAM-1(tm1Jcgr) mice have impaired thymocyte development. Proportions and numbers of double negative, double positive, mature CD4(+) and CD8(+) thymocytes, as well as of regulatory T (Treg) cells were also significantly decreased. In the periphery, ICAM-1(tm1Jcgr) mice had significantly decreased proportions and numbers of naive and activated/memory CD4(+) and CD8(+) T cells, as well as of Treg cells, in lymph nodes but not in the spleen. In vitro activation of CD4(+) and CD8(+) T cells from ICAM-1(tm1Jcgr) mice with anti-CD3 antibodies and antigen-presenting cells (APCs) resulted in a significantly weaker proliferation, whereas proliferation induced with anti-CD3 and anti-CD28 antibody-coated beads was normal. In vivo immunization of ICAM-1(tm1Jcgr) mice resulted in normal generation of specific effector and memory immune responses that protect against a viral challenge. However, contrary to ICAM-1(WT) mice, immunization-induced specific effectors could not eradicate immunogen-expressing tumours. Treg cells from ICAM-1(tm1Jcgr) mice have abnormal activation and proliferation induced by anti-CD3 antibody and APCs, and have markedly decreased suppressive activity in vitro. In contrast to ICAM-1(WT) mice, they were unable to control experimentally induced colitis in vivo. Hence, our results further highlight the pleiotropic role of ICAM-1 in T-cell-dependent immune responses, with a major role in Treg cell development and suppressive function.

Sustained stimulation and expansion of Tregs by IL2 control autoimmunity without impairing immune responses to infection, vaccination and cancer.

Interleukin 2 (IL2) is the key cytokine supporting survival and function of regulatory T cells (Tregs). We recently reported that low-dose IL2 safely expands/stimulates Tregs and improves autoimmune conditions in humans. Further development of IL2 in autoimmune diseases will require chronic IL2 administration, which could affect beneficial effector immune responses regulated by Tregs. We used recombinant adeno-associated viral vector (rAAV)-mediated gene transfer to continuously release IL2 in mice and assessed its long-term effects on immune responses. A single rAAV-IL2 injection enabled sustained stimulation and expansion of Tregs without inducing Teff activation and prevented diabetes in NOD mice. After several weeks of IL2 production, mice responded normally to a viral challenge and to vaccination, and had pregnancies with offspring that developed normally. They showed no change in the occurrence and growth of chemically-induced tumors. Altogether, chronic low-dose IL2 treatment does not affect beneficial effector immune responses at doses that prevent autoimmune diabetes.

Intrathymic injection of lentiviral vector curtails the immune response in the periphery of normal mice.

BACKGROUND: Gene transfer in the thymus, based on HIV-derived lentiviral vectors, is a promising avenue for modulation of T cell selection and autoimmunity. However, the impact of intrathymic (IT) injections on an antigen-specific immune response elicited in the periphery of normal mice has not been investigated yet. METHODS: Highly concentrated stocks of lentiviral vectors expressing the soluble form of hemaglutinin of the influenza virus (LvHA) were injected in the thymus of normal BALB/c mice. The CD4 and CD8-mediated immune responses to HA after peripheral immunization were measured by various parameters. RESULTS: We first show that a lentiviral vector expressing the luciferase was detected for at least 2 months after IT-injections. We then show that the LvHA vector could elicit a functional CD4- and CD8-T cell-mediated immune responses in the peripheral lymphoid organs of BALB/c mice. IT-injection of the LvHA vector significantly curbed this response: lower numbers of transferred HA-specific CD4(+) T cells were found in LvHA-injected compared to control animals. Furthermore, lower frequencies of HA-specific CD8(+) T cells, interferon γ-producing cells and cytotoxic cells were detected from 3 weeks to 3 months in LvHA-injected mice compared to controls. However, these reduced CD8-mediated responses were not increased after depletion of CD25(+) cells in vitro or in vivo. CONCLUSIONS: The results obtained in the present study show that injection of the LvHA lentiviral vector significantly curtailed the immune response to the same antigen in the periphery. Increased selection of HA-specific regulatory T cells and negative selection of HA-specific CD8(+) T cell precursors may explain the results. Our work establish the feasibility of IT-injections of lentiviral vectors to manipulate T cell tolerance in the thymus of normal mice, for basic and pre-clinical research.

Immunological environment in colorectal cancer: a computer-aided morphometric study of whole slide digital images derived from tissue microarray.

Cancer research has moved from investigating tumour cells to including analysis of the tumour microenvironment as well. The aim of this study was to assess the cellular infiltrate of colorectal cancer (CRC) using computer-aided analysis of whole slide digital image derived from tissue microarray (TMA). TMA slides from 31 CRC patients were immunostained for forkhead box protein 3 (FOXP3) and immunomodulatory enzyme indoleamine 2,3-dioxygenase (IDO) at four sites: centre (C) and invasive front (F) of the tumour, proximal non-metastatic draining lymph node (N-), tumour-draining lymph node with metastasis (N+) and healthy mucosa at 10 cm from the cancer (M). We analysed the proportion of IDO+ tissue areas in the lamina propria or in the non-epithelial area of the lymph node and in epithelial cells in each site. The normal mucosa of patients operated on for benign disease was also analysed. The proportion (%) of FOXP3+ tissue area in C, F, N-, N+ and M were 2.3 ± 1.8, 2.6 ± 2.9, 6.0 ± 2.9, 14.2 ± 5.8 and 1.2 ± 0.8 (p < 0.001). The proportion (%) of IDO+ tissue area in the lamina propria of C, F, N-, N+ and M were 1.6 ± 3.1, 1.1 ± 1.3, 3.4 ± 2.5, 9.1 ± 8.5 and 6.7 ± 5.4 (p < 0.001). IDO+ tissue area in the lamina propria was not significantly different between healthy mucosa of patients with cancer than without (1.8 ± 3 vs 1.1 ± 0.95). The proportion of IDO positive tissue area in the epithelium was significantly higher in healthy mucosa of patients with cancer than without (5.4 ± 13.8 vs 2.1 ± 2.4). The FOXP3+ tissue area was increased in healthy mucosa of CRC patients in comparison with healthy mucosa of patients with colorectal resection for disease other than cancer: 1.20 ± 1.81 versus 0.81 ± 0.51 (p < 0.05). The proportion of IDO+ tissue area in lymph node (N-) was correlated with the proportion of FOXP3+ tissue area in tumour area (r = 0.44, p < 0.01). TMA technique permits simultaneous analysis of FOXP3+ and IDO+ cells at different sites including tumour, draining non-metastatic lymph node, metastatic lymph node and normal mucosa.