SUMMARYHelicobacter pylori induces symptomatic chronic gastritis in a subpopulation of infected individuals. The mechanism(s) determining the development and severity of pathology leading to symptoms are not fully understood. In a mouse model of H. pylori infection we analysed the influence of immunoregulatory CD4 + CD25 + T cells on H. pylori colonization and gastritis. Athymic C57BL/6 nu/nu mice were reconstituted with (a) lymph node (LN) cells (b) LN cells depleted of CD25 + T cells (CD25 -LN) or (c) not reconstituted at all. Mice were then infected orally with 3 ¥ 10 8 H. pylori SS1 bacteria. At 2 and 6 weeks after the inoculation there was a significant ( P < 0·001) reduction in H. pylori colonization in athymic mice transferred with CD25 -LN cells compared to mice transferred with LN cells. Colonization was still reduced at 12 weeks after inoculation. Mice transferred with CD25 -LN cells showed an earlier onset and increased severity of gastritis as compared to mice receiving LN cells. Splenic cells isolated from mice receiving CD25 -LN cells produced the highest level of IFN-g on stimulation with H. pylori antigens in vitro, had a higher H. pylori -specific DTH response and increased infiltration of CD4 + T cells and macrophages in the gastric mucosa. Athymic mice not transferred with T cells had persistent high H. pylori colonization and displayed a normal gastric epithelium without inflammatory cells. In conclusion, CD4 + CD25 + cells reduce immunopathology in H. pylori infection, possibly by reducing the activation of IFN-g producing CD4 + T cells, even at the expense of a higher H. pylori load in the gastric mucosa.

Oral administration of Ag coupled to cholera toxin B subunit (CTB) efficiently induces peripheral immunological tolerance. We investigated the extent to which this oral tolerance is mediated by CD25+CD4+ regulatory T cells (Treg). We found that total Treg, KJ1–26+ Treg and CTLA-4+ Treg were all increased in Peyer’s patches, mesenteric lymph nodes, and, to a lesser extent, in spleen of mice after intragastric administration of OVA/CTB conjugate, which also increased TGF-β in serum. This could be abolished by coadministering cholera toxin or by treatment with anti-TGF-β mAb. CD25+ Treg, but also CD25−CD4+ T cells from OVA/CTB-treated BALB/c or DO11.10 mice efficiently suppressed effector T cell proliferation and IL-2 production in vitro. Following adoptive transfer, both T cell populations also suppressed OVA-specific T cell and delayed-type hypersensitivity responses in vivo. Foxp3 was strongly expressed by CD25+ Treg from OVA/CTB-treated mice, and treatment also markedly expanded CD25+Foxp3+ Treg. Furthermore, in Rag1−/− mice that had adoptively received highly purified Foxp3−CD25−CD4+ OT-II T cells OVA/CTB feeding efficiently induced CD25+ Treg cells, which expressed Foxp3 more strongly than naturally developing Treg and also had stronger ability to suppress effector OT-II T cell proliferation. A remaining CD25− T cell population, which also became suppressive in response to OVA/CTB treatment, did not express Foxp3. Our results demonstrate that oral tolerance induced by CTB-conjugated Ag is associated with increase in TGF-β and in both the frequency and suppressive capacity of Foxp3+ and CTLA-4+ CD25+ Treg together with the generation of both Foxp3+ and Foxp3−CD25− CD4+ Treg.

BackgroundRheumatoid arthritis is a chronic inflammatory disease with a strong MHC class II component and where many patients develop characteristic autoantibodies towards the noncoding amino acid citrulline. Such anti-citrullinated protein antibodies (ACPA) have recently been put forward as an independent predictive factor for treatment response by co-stimulation blockade by CTLA4-Ig (abatacept). We have performed a mechanism of action study to dissect T cell functionality in RA patients with long-standing disease undergoing abatacept treatment and the influence of ACPA status.ResultsPeripheral blood samples were collected from RA patients as they started CTLA4-Ig treatment and 3 and 6 months later. A general decrease of regulatory T cell subsets was observed in the cohort. Additionally within the ACPA-positive group significant down-regulation of all key T cell effector subsets including Th1, Th2, and Th17 was observed by analyzing cytokines by intracellular flow cytometry and in cell culture supernatants.RA synovial fluid samples were cultured in vitro in the presence or absence of CTLA4-Ig (abatacept). T cell cytokine production was diminished, but without increasing the functional capacity of CD4+CD25hi regulatory T cells as previously demonstrated in the context of TNF-blockade and anti-IL6R therapy.ConclusionsOur immunological study of T cell functionality in RA patients, both ACPA-positive and ACPA-negative, starting biological therapy with the co-stimulation blockade abatacept (CTLA4-Ig) supports the recently published registry study implicating ACPA seropositivity as an independent predictive factor to treatment response as we observed the most striking effect on T cell subset modulation in ACPA-positive patients. These data further support the notion of RA as a disease with several sub-entities, where the ACPA-positive fraction represents a classical HLA-associated autoimmune disorder while ACPA-negative patients may have other driving forces apart from classical adaptive immune responses.

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