Manipulation of Th responses by oral tolerance

Research advances in the imbalance of helper T lymphocyte subpopulations and cytokine network in patients with chronic hepatitis B

Helper T (Th) lymphocytes, important immune regulating cells of organism, could be divided into four functional subsets, Th0, Th1, Th2, Th3, on the basis of the immunoregulatory cytokines that these clones produced. Most of the current work in this field is exploratory and focuses on Th1 and Th2 subsets. Th1 cells secrete interferon-γ (IFN-γ), interkeukin-2 (IL-2) and tumor necrosis factor-β and are principally involved in cell-mediated immunity. They play an important role in the protection against intracellular pathogens, including a variety of viruses. Th2 cells secret interleukin-4 (IL-4), IL-5, IL-6 and IL-10 and regulate the humoral immune response. Th0 cells are naive Th cells, secreting Th1/Th2 phenotype cytokines at low levels. However, Th3 cells, which secrete active transforming growth factor-β, exert a negative immunoregulatory action on the immune response. The cross-regulatory properties of Th1 and Th2 subset cells and relevant cytokines network are very important to maintain normal immunity of organisms. HBV can destroy the balance of Th lymphocytes and cytokines network. The imbalance of pro-inflammatory Th1 and anti-inflammatory Th2 cytokine production play an important role in the immunopathogenesis of hepatitis B virus infection and alter chronic liver disease development, progression and outcome.

Role of autoimmunity in organ allograft rejection: a focus on immunity to type V collagen in the pathogenesis of lung transplant rejection

Lung transplantation is the only definitive treatment modality for many forms of end-stage lung disease. However, the lung is rejected more often than any other type of solid organ allograft due to chronic rejection known as bronchiolitis obliterans (BO). Indeed, BO is the primary reason why the 5- and 7-yr survival rates are worse for the lung than for any other transplanted organ. Alloimmunity to donor antigens is established as the primary mechanism that mediates rejection responses. However, newer immunosuppressive regimens designed to abrogate alloimmune activation have not improved survival. Therefore, these data suggest that other antigens, unrelated to donor transplantation antigens, are involved in rejection. Utilizing human and rodent studies of lung transplantation, our laboratory has documented that a native collagen, type V collagen [col(V)], is a target of the rejection response. Col(V) is highly conserved; therefore, these data indicate that transplant rejection involves both alloimmune and autoimmune responses. The role of col(V) in lung transplant rejection is described in this review article. In addition, the potential role of regulatory T cells that are crucial to modulating autoimmunity and alloimmunity is also discussed.

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Retroviral gene therapy with an immunoglobulin-antigen fusion construct protects from experimental autoimmune uveitis

Immunoglobulins can serve as tolerogenic carriers for antigens, and B cells can function as tolerogenic antigen-presenting cells. We used this principle to design a strategy for gene therapy of experimental autoimmune uveitis, a cell-mediated autoimmune disease model for human uveitis induced with the uveitogenic interphotoreceptor retinoid-binding protein (IRBP). A retroviral vector was constructed containing a major uveitogenic IRBP epitope in frame with mouse IgG1 heavy chain. This construct was used to transduce peripheral B cells, which were infused into syngeneic recipients. A single infusion of transduced cells, 10 days before uveitogenic challenge, protected mice from clinical disease induced with the epitope or with the native IRBP protein. Protected mice had reduced antigen-specific responses, but showed no evidence for a classic Th1/Th2 response shift or for generalized anergy. Protection was not transferable, arguing against a mechanism dependent on regulatory cells. Importantly, the treatment was protective when initiated 7 days after uveitogenic immunization or concurrently with adoptive transfer of primed uveitogenic T cells. We suggest that this form of gene therapy can induce epitope-specific protection not only in naive, but also in already primed recipients, thus providing a protocol for treatment of established autoimmunity.