CD40-activated B cells are more potent than immature dendritic cells to induce and expand CD4(+) regulatory T cells

Comparison of antibody and T-cell responses elicited by licensed inactivated- and live-attenuated influenza vaccines against H3N2 hemagglutinin

T cells are being increasingly recognized as a significant component of influenza-specific immune responses in humans. Although an inactivated- and a live-attenuated influenza vaccine are now licensed for use in humans, their comparative ability to elicit T-cell responses against influenza is not well understood. Using the rapidly evolving H3N2 hemagglutinin (HA) as an antigenic model, we compared immune responses elicited by the trivalent inactivated influenza vaccine (TIV) and the live-attenuated influenza vaccine (LAIV) in a cohort of healthy adults 18-49 years of age. TIV elicited higher geometrical mean antibody titers than LAIV, whereas, LAIV elicited superior T-cell responses. Importantly, LAIV elicited higher magnitude T-cell responses toward the rapidly drifting variant region of HA that is prone to escape from antibody responses. These results have important implications for the deployment of influenza vaccines in years of antigenic mismatch and shift.

Generation of human Th1-like regulatory CD4+ T cells by an intrinsic IFN-γ- and T-bet-dependent pathway

Murine Foxp3(+) Treg have recently been shown to express T-bet, a transcription factor characteristic of Th1 effector cells. A human Treg phenotype equivalent has not been reported. Here, we show that naïve human CD4(+) T cells incubated with low numbers of CD40-activated allogeneic B cells preferentially differentiate into alloantigen-specific CD4(hi) CD25(hi) Treg. These differentiated cells potently suppress effector T-cell responses and express T-bet, IFN-γ, and CXCR3, the features of Th1 effector cells. In contrast, co-culture of naïve CD4(+) T cells with high numbers of allogeneic B cells results in CD4(+) CD25(+) T cells that promote, rather than inhibit, effector T-cell responses, demonstrating the plasticity of CD4(+) T-cell differentiation in response to alloantigen-presenting B cells. The optimal accumulation of CD4(hi) CD25(hi) Treg induced using higher T cell:B cell co-culture ratios was dependent on the expression of T-bet and endogenously produced IFN-γ. Induction of Treg-mediated suppression function in the Treg population was not. As CXCR3 confers the preferential trafficking of T cells to tissue sites of IFN-γ, these human Th1-like Treg might be useful for modulating pathological Th1 effector responses, such as that occurring during graft-versus-host disease or graft rejection.

Antileukemia and antitumor effects of the graft-versus-host disease: a new immunovirological approach

In leukemic mice, the native host's explicit and well-defined immune reactions to the leukemia virus (a strong exogenous antigen) and to leukemia cells (pretending in their native hosts to be protected "self" elements) are extinguished and replaced in GvHD (graft-versus-host disease) by those of the immunocompetent donor cells. In many cases, the GvHD-inducer donors display genetically encoded resistance to the leukemia virus. In human patients only antileukemia and anti-tumor cell immune reactions are mobilized; thus, patients are deprived of immune reactions to a strong exogenous antigen (the elusive human leukemia-sarcoma retroviruses). The innate and adaptive immune systems of mice have to sustain the immunosuppressive effects of leukemia-inducing retroviruses. Human patients due to the lack of leukemiainducing retroviral pathogens (if they exist, they have not as yet been discovered), escape such immunological downgrading. After studying leukemogenic retroviruses in murine and feline (and other mammalian) hosts, it is very difficult to dismiss retroviral etiology for human leukemias and sarcomas. Since no characterized and thus recognized leukemogenic-sarcomagenic retroviral agents are being isolated from the vast majority of human leukemias-sarcomas, the treatment for these conditions in mice and in human patients vastly differ. It is immunological and biological modalities (alpha interferons; vaccines; adoptive lymphocyte therapy) that dominate the treatment of murine leukemias, whereas combination chemotherapy remains the main remission-inducing agent in human leukemias-lymphomas and sarcomas (as humanized monoclonal antibodies and immunotoxins move in). Yet, in this apparently different backgrounds in Mus and Homo, GvHD, as a treatment modality, appears to work well in both hosts, by replacing the hosts' anti-leukemia and anti-tumor immune faculties with those of the donor. The clinical application of GvHD in the treatment of human leukemias-lymphomas and malignant solid tumors remains a force worthy of pursuit, refinement and strengthening. Graft engineering and modifications of the inner immunological environment of the recipient host by the activation or administration of tumor memory T cells, selected Treg cells and natural killer (NKT) cell classes and cytokines, and the improved pharmacotherapy of GvHD without reducing its antitumor efficacy, will raise the value of GvHD to the higher ranks of the effective antitumor immunotherapeutical measures. Clinical interventions of HCT/HSCT (hematopoietic cell/stem cell transplants) are now applicable to an extended spectrum of malignant diseases in human patients, being available to elderly patients, who receive non-myeloablative conditioning, are re-enforced by post-transplant donor lymphocyte (NK cell and immune T cell) infusions and post-transplant vaccinations, and the donor cells may derive from engineered grafts, or from cord blood with reduced GvHD, but increased GvL/GvT-inducing capabilities (graft-versus leukemia/tumor). Post-transplant T cell transfusions are possible only if selected leukemia antigen-specific T cell clones are available. In verbatim quotation: "Ultimately, advances in separation of GvT from GvHD will further enhance the potential of allogeneic HCT as a curative treatment for hematological malignancies" (Rezvani, A.R. and Storb, R.F., Journal of Autoimmunity 30:172-179, 2008 (see in the text)). It may be added: for cure, a combination of the GvL/T effects with new targeted therapeutic modalities, as elaborated on in this article, will be necessary.

Regulation of immunity and autoimmunity by B cells

Compelling evidence has demonstrated that IL-10-producing regulatory B cells (B(regs)) are specialized to suppress immune responses and control various immunopathologies. Several reports have provided information on the phenotype, generation, and mechanism of action of B(regs). Recent work has also identified B(regs) in humans and has begun to unravel their phenotype and mode of suppression. A complete analysis of their function in immune-mediated diseases is required for possible future use of B(regs) as a part of new clinical strategies for treating autoimmune diseases and in the induction of transplant tolerance.

Regulatory B cells in autoimmunity: developments and controversies

Over a decade has now passed since the concept of B cells with a regulatory function was resurrected--B cells that produce antibodies with a suppressive effect were first reported in the 1960s and suppressor B cells in the 2000s. In the meantime, some aspects of regulatory B (B(REG))-cell biology have been elucidated. Not only have scientists begun to unravel the mechanism of how B(REG) cells suppress immune responses and which cells they target, but their ontogeny and development has also begun to be determined. To date, key roles for B(REG) cells have been identified in the regulation of several immune-mediated processes, including autoimmunity and responses to infectious disease and cancer. This Review highlights these advances in the study of B(REG) cells, and outlines what is known about their phenotype as well as their suppressive role in autoimmunity from studies in both mice and humans. A particular emphasis is placed on B(REG)-cell function in rheumatic diseases.

CD40: novel association with Crohn's disease and replication in multiple sclerosis susceptibility

BACKGROUND

A functional polymorphism located at -1 from the start codon of the CD40 gene, rs1883832, was previously reported to disrupt a Kozak sequence essential for translation. It has been consistently associated with Graves' disease risk in populations of different ethnicity and genetic proxies of this variant evaluated in genome-wide association studies have shown evidence of an effect in rheumatoid arthritis and multiple sclerosis (MS) susceptibility. However, the protective allele associated with Graves' disease or rheumatoid arthritis has shown a risk role in MS, an effect that we aimed to replicate in the present work. We hypothesized that this functional polymorphism might also show an association with other complex autoimmune condition such as inflammatory bowel disease, given the CD40 overexpression previously observed in Crohn's disease (CD) lesions.

METHODOLOGY

Genotyping of rs1883832C>T was performed in 1564 MS, 1102 CD and 969 ulcerative colitis (UC) Spanish patients and in 2948 ethnically matched controls by TaqMan chemistry.

PRINCIPAL FINDINGS

The observed effect of the minor allele rs1883832T was replicated in our independent Spanish MS cohort [p = 0.025; OR (95% CI) = 1.12 (1.01-1.23)]. The frequency of the minor allele was also significantly higher in CD patients than in controls [p = 0.002; OR (95% CI) = 1.19 (1.06-1.33)]. This increased predisposition was not detected in UC patients [p = 0.5; OR (95% CI) = 1.04 (0.93-1.17)].

CONCLUSION

The impact of CD40 rs1883832 on MS and CD risk points to a common signaling shared by these autoimmune conditions.

Cytotoxic T lymphocytes established by seasonal human influenza cross-react against 2009 pandemic H1N1 influenza virus

While few children and young adults have cross-protective antibodies to the pandemic H1N1 2009 (pdmH1N1) virus, the illness remains mild. The biological reasons for these epidemiological observations are unclear. In this study, we demonstrate that the bulk memory cytotoxic T lymphocytes (CTLs) established by seasonal influenza viruses from healthy individuals who have not been exposed to pdmH1N1 can directly lyse pdmH1N1-infected target cells and produce gamma interferon (IFN-gamma) and tumor necrosis factor alpha (TNF-alpha). Using influenza A virus matrix protein 1 (M1(58-66)) epitope-specific CTLs isolated from healthy HLA-A2(+) individuals, we further found that M1(58-66) epitope-specific CTLs efficiently killed both M1(58-66) peptide-pulsed and pdmH1N1-infected target cells ex vivo. These M1(58-66)-specific CTLs showed an effector memory phenotype and expressed CXCR3 and CCR5 chemokine receptors. Of 94 influenza A virus CD8 T-cell epitopes obtained from the Immune Epitope Database (IEDB), 17 epitopes are conserved in pdmH1N1, and more than half of these conserved epitopes are derived from M1 protein. In addition, 65% (11/17) of these epitopes were 100% conserved in seasonal influenza vaccine H1N1 strains during the last 20 years. Importantly, seasonal influenza vaccination could expand the functional M1(58-66) epitope-specific CTLs in 20% (4/20) of HLA-A2(+) individuals. Our results indicated that memory CTLs established by seasonal influenza A viruses or vaccines had cross-reactivity against pdmH1N1. These might explain, at least in part, the unexpected mild pdmH1N1 illness in the community and also might provide some valuable insights for the future design of broadly protective vaccines to prevent influenza, especially pandemic influenza.