T-cell Independent Immune Responses Research Articles

The immunomodulatory effect of koumine on B cells under dependent and independent responses by T cells

Dysregulated activation of polyclonal B cells and production of pathogenic antibodies are involved in the development of rheumatoid arthritis (RA). Therefore, targeted B cell therapy is effective against RA. Gelsemium elegans (Gardn. & Champ.) Benth., a toxic plant widely distributed in Southeast Asia, has been used for treating rheumatoid pain, neuropathic pain, spasticity, skin ulcers, and cancers for many years in traditional Chinese medicine. Koumine, an alkaloid monomer from Gelsemium elegans Benth., exerts therapeutic effects against RA. However, whether koumine affects B cells remains unknown. In this study, the effect of koumine on B cells under T cell-independent (TI) and T cell-dependent (TD) immune responses is investigated in vitro and in vivo. Mouse primary B cells were obtained by immunomagnetic bead sorting, and immunomodulatory effects of koumine on the activation, proliferation, and differentiation of B cells were determined in TI and TD models induced by lipopolysaccharide (LPS) and anti-CD40 antibodies in vitro, respectively. The humoral immune responses of TI and TD were established using NP-AECM-FICOLL and NP-CGG in C57BL/6J mice, respectively. We found that koumine inhibited B cell differentiation in the TI model and inhibited B cell activation and proliferation in the TD model in vitro. Koumine also inhibited antibody secretion in TI immune response, TD initial immune response, and in TD secondary immune response. Our results reveal that koumine has a direct and indirect immune regulatory effect on B cells, showing that it can directly inhibit the differentiation and secretion of autoantibodies after abnormal activation of B cells, and indirectly inhibit the activation and proliferation of TD B cells to reduce the secretion of antibodies. It may be an important mechanism for its anti-RA effect in mice, providing a rationale and laboratory data support for the application of koumine in anti-human RA therapy.

IgM Memory B Cell Heterogeneity in Immune Responses to Pneumococcal Vaccination in HIV-positive and Healthy Individuals

Abstract Background: Both normal aging and HIV infection impact B cell functionality and lead to activation of resting B cells, memory cell depletion and altered gene expression. As a result, HIV+ individuals and the elderly fail to demonstrate robust and durable immune responses against pneumococcal polysaccharides. Herein, we assessed altered B cell function in high risk groups by utilizing single cell technology. Methods: HIV-positive individuals with CD4+T cell counts >200 on Antiretroviral Therapy (ART) and HIV-negative individuals age groups 21-40 and 50-65 received pneumococcal vaccination. Serum IgG and IgM PPS-specific antibodies were measured pre- and post-immunization using ELISA method. Evaluation of B cells was performed using flow cytometry and single cell RT-PCR. Results: IgM memory B cells are important players in responding to pneumococcal antigens and are present in reduced quantities in HIV+ and aging HIV- individuals. Single cell analysis of IgM memory B cells demonstrated heterogeneity and identified two unique subpopulations. One of the subpopulations represents B cells with higher expression of TACI and BAFF-R and is more likely to dominate in T-cell independent immune responses. IgD+IgM+memory B cells were present in equal proportions in both subpopulations. Conclusion: Pneumococcal vaccine responses in HIV+ and aging HIV- individuals are multifactorial and largely depend on the abundance and phenotypic characteristics of IgM memory B cells.

The Role of Interleukin-10 in Mediating the Effect of Immune Challenge on Mouse Gonadotropin-Releasing Hormone Neurons In Vivo.

Immune challenge alters neural functioning via cytokine production. Inflammation has profound impact on the central regulation of fertility, but the mechanisms involved are not clearly defined. The anti-inflammatory cytokine interleukin (IL)-10 is responsible for balancing the immune response in the brain. To examine whether IL-10 has an effect on the function of the gonadotropin-releasing hormone (GnRH) neurons, we first examined the effect of immune responses with distinct cytokine profiles, such as the T cell-dependent (TD) and T cell-independent (TI) B-cell response. We investigated the effect of the TD and TI immune responses on ERK1/2 phosphorylation in GnRH neurons by administering fluorescein isothiocyanate/keyhole limpet hemocyanin (KLH-FITC) or dextran-FITC to female mice. Although dextran-FITC had no effect, KLH-FITC induced ERK1/2 phosphorylation in GnRH neurons after 6 d. KLH-FITC treatment increased the levels of IL-10 in the hypothalamus (HYP), but this treatment did not cause lymphocyte infiltration or an increase in the levels of proinflammatory cytokines. In IL-10 knock-out (KO) mice, KLH-FITC-induced ERK1/2 phosphorylation in the GnRH neurons was absent. We also showed that in IL-10 KO mice, the estrous cycle was disrupted. Perforated patch-clamp recordings from GnRH-GFP neurons, IL-10 immunohistochemistry, and in vitro experiments on acute brain slices revealed that IL-10 can directly alter GnRH neuron firing and induce ERK1/2 phosphorylation. These observations demonstrate that IL-10 plays a role in influencing signaling of GnRH neurons in the TD immune response. These results also provide the first evidence that IL-10 can directly alter the function of GnRH neurons and may help the maintenance of the integrity of the estrous cycle.

Reduced Number of Transitional and Naive B Cells in Addition to Decreased BAFF Levels in Response to the T Cell Independent Immunogen Pneumovax®23.

Protective immunity against T cell independent (TI) antigens such as Streptococcus pneumoniae is characterized by antibody production of B cells induced by the combined activation of T cell independent type 1 and type 2 antigens in the absence of direct T cell help. In mice, the main players in TI immune responses have been well defined as marginal zone (MZ) B cells and B-1 cells. However, the existence of human equivalents to these B cell subsets and the nature of the human B cell compartment involved in the immune reaction remain elusive. We therefore analyzed the effect of a TI antigen on the B cell compartment through immunization of healthy individuals with the pneumococcal polysaccharide (PnPS)-based vaccine Pneumovax®23, and subsequent characterization of B cell subpopulations. Our data demonstrates a transient decrease of transitional and naïve B cells, with a concomitant increase of IgA+ but not IgM+ or IgG+ memory B cells and a predominant generation of PnPS-specific IgA+ producing plasma cells. No alterations could be detected in T cells, or proposed human B-1 and MZ B cell equivalents. Consistent with the idea of a TI immune response, antigen-specific memory responses could not be observed. Finally, BAFF, which is supposed to drive class switching to IgA, was unexpectedly found to be decreased in serum in response to Pneumovax®23. Our results demonstrate that a characteristic TI response induced by Pneumovax®23 is associated with distinct phenotypical and functional changes within the B cell compartment. Those modulations occur in the absence of any modulations of T cells and without the development of a specific memory response.

Synthesis of tumor-associated MUC1-glycopeptides and their multivalent presentation by functionalized gold colloids.

The mucin MUC1 is a glycoprotein involved in fundamental biological processes, which can be found over-expressed and with a distinctly altered glycan pattern on epithelial tumor cells; thus it is a promising target structure in the quest for effective carbohydrate-based cancer vaccines and immunotherapeutics. Natural glycopeptide antigens indicate only a low immunogenicity and a T-cell independent immune response; however, this major drawback can be overcome by coupling of glycopeptide antigens multivalently to immunostimulating carrier platforms. In particular, gold nanoparticles are well suited as templates for the multivalent presentation of glycopeptide antigens, due to their remarkably high surface-to-volume ratio in combination with their high biostability. In this work the synthesis of novel MUC1-glycopeptide antigens and their coupling to gold nanoparticles of different sizes are presented. In addition, the development of a new dot-blot immunoassay to test the potential antigen-antibody binding is introduced.

T cell–independent B cell activation induces immunosuppressive sialylated IgG antibodies

Antigen-specific Abs are able to enhance or suppress immune responses depending on the receptors that they bind on immune cells. Recent studies have shown that pro- or antiinflammatory effector functions of IgG Abs are also regulated through their Fc N-linked glycosylation patterns. IgG Abs that are agalactosylated (non-galactosylated) and asialylated are proinflammatory and induced by the combination of T cell-dependent (TD) protein antigens and proinflammatory costimulation. Sialylated IgG Abs, which are immunosuppressive, and Tregs are produced in the presence of TD antigens under tolerance conditions. T cell-independent (TI) B cell activation via B cell receptor (BCR) crosslinking through polysaccharides or via BCR and TLR costimulation also induces IgG Abs, but the Fc glycosylation state of these Abs is unknown. We found in mouse experiments that TI immune responses induced suppressive sialylated IgGs, in contrast to TD proinflammatory Th1 and Th17 immune responses, which induced agalactosylated and asialylated IgGs. Transfer of low amounts of antigen-specific sialylated IgG Abs was sufficient to inhibit B cell activation and pathogenic immune reactions. These findings suggest an immune regulatory function for TI immune responses through the generation of immunosuppressive sialylated IgGs and may provide insight on the role of TI immune responses during infection, vaccination, and autoimmunity.

Spontaneous Development of IgM Anti‐Cocaine Antibodies in Habitual Cocaine Users: Effect on IgG Antibody Responses to a Cocaine Cholera Toxin B Conjugate Vaccine

In cocaine vaccine studies, only a minority of subjects made strong antibody responses. To investigate this issue, IgG and IgM antibody responses to cocaine and to cholera toxin B (CTB-the carrier protein used to enhance immune responses to cocaine) were measured in sera from the 55 actively vaccinated subjects in a Phase IIb randomized double-blind placebo-controlled trial (TA-CD 109). Isotype specific ELISAs were used to measure IgG and IgM anti-cocaine and anti-CTB antibody in serial samples collected prior to and at intervals after immunization. We assessed IgG anti-cocaine responses of patients with pre-vaccination IgM anti-cocaine antibodies. Competitive inhibition ELISA was used to evaluate antibody specificity. Before immunization, 36/55 subjects had detectable IgM antibodies to cocaine, and 9 had IgM levels above the 95% confidence limit of 11 μg/ml. These nine had significantly reduced peak IgG anti-cocaine responses at 16 weeks, and all were below the concentration (40 μg/ml) considered necessary to discourage recreational cocaine use. The IgG anti-CTB responses of these same subjects were also reduced. Subjects who develop an IgM antibody response to cocaine in the course of repeated recreational exposure to this drug are significantly less likely to produce high levels of IgG antibodies from the cocaine conjugate vaccine. The failure may be due to recreational cocaine exposure induction of a type 2 T-cell independent immune response. Such individuals will require improved vaccines and are poor candidates for the currently available vaccine.

Development of New Vaccines against Meningococcal Disease

Meningococcal diseases continue to have a major public health impact in many countries. Five major groups of Neisseria meningitidis (A, B, C, Y and W135) are responsible for most meningoccocal diseases. Plain polysaccharides vaccines for Nelsseria meningitidis groups A, C, Y and W-135 have been in use for approximately 20 years, both to prevent invasive disease in high-risk population and to control disease outbreaks. However, these conventional meningococcal vaccines induce a relatively short-lasting T-cell independent immune response, are not effective in children under two years of age and can induce hyporesponsiveness. New meningococcal group C conjugate vaccines have since been developed, which offer solid advantages over the currently licensed plain polysaccharide vaccines. There is still no vaccine available against the serogroup B, which is a major cause of invasive disease. This report summarises the different approaches to the development of vaccines against the pathogenic meningococci.

Three different expression patterns of T-bet in angioimmunoblastic T-cell lymphoma

Angioimmunoblastic T-cell lymphoma (AITL) exhibits a multifaceted clinical picture and distinct architectural patterns that correlate with disease progression and the number of neoplastic cells. In this study we investigated the expression of the transcription factor T-bet and correlated it with the architectural patterns in 29 cases of AITL. Double immunolabelings for T-bet, CD20, CD3 or PD1 revealed the following patterns: predominant T-bet expression by neoplastic T-cells (A), by aggregates of small B-cells (B) or by B-immunoblasts (C). The majority of cases of AITL pattern II showed a T-bet expression pattern B (6/8 cases), while the majority of those with pattern III exhibited the T-bet pattern A (11/21 cases). We propose that T-bet expression by B-cells represents a T-cell independent immune response trying to cope with opportunistic infections, while T-bet expression by neoplastic T-cells is linked to the introduction of a Th17 response responsible for the immunologic derangements characteristic of AITL.

On the role of persistent signaling and autocatalysis in the T-cell independent immune response

A kinetic model of the T-cell independent immune response is presented which includes two new mechanistic features. First, a persistent signaling mechanism is hypothesized which requires that proliferating cell receptor sites be continuously occupied in order for mitotic proliferation to occur. Second, an autocatalytic mechanism is introduced (coupled with the persistent signaling mechanism) which results in rapid termination of the B-cell response upon sufficient reduction of the antigen population.