Lipid Mediators From Timothy Grass Pollen Contribute to the Effector Phase of Allergy and Prime Dendritic Cells for Glycolipid Presentation.

Plant pollen are an important source of antigens that evoke allergic responses. Protein antigens have been the focus of studies aiming to elucidate the mechanisms responsible for allergic reactions to pollen. However, proteins are not the sole active agent present in pollen. It is known that pollen grains contain lipids essential for its reproduction and bioactive lipid mediators. These small molecular compounds are co-delivered with the allergens and hence have the potential to modulate the immune response of subjects by activating their innate immune cells. Previous reports showed that pollen associated lipid mediators exhibited neutrophil- and eosinophil-chemotactic activity and induced polarization of dendritic cells (DCs) toward a Th2-inducing phenotype. In our study we performed chemical analyses of the pollen associated lipids, that are rapidly released upon hydration. As main components we have identified different types of phytoprostanes (PhytoPs), and for the first time phytofurans (PhytoFs), with predominating 16-F1t-PhytoPs (PPF1-I), 9-F1t-PhytoPs (PPF1-II), 16-E1t-PhytoPs (PPE1-I) and 9-D1t-PhytoPs (PPE1-II), and 16(RS)-9-epi-ST-Δ14-10-PhytoFs. Interestingly 16-E1t-PhytoP and 9-D1t-PhytoPs were found to be bound to glycerol. Lipid-containing samples (aqueous pollen extract, APE) induced murine mast cell chemotaxis and IL-6 release, and enhanced their IgE-dependent degranulation, demonstrating a role for these lipids in the immediate effector phase of allergic inflammation. Noteworthy, mast cell degranulation seems to be dependent on glycerol-bound, but not free phytoprostanes. On murine dendritic cells, APE selectively induced the upregulation of CD1d, likely preparing lipid-antigen presentation to iNKT cells. Our report contributes to the understanding of the activity of lipid mediators in the immediate effector phase of allergic reactions but identifies a yet undescribed pathway for the recognition of pollen-derived glycolipids by iNKT cells.

Argemone oil, an edible oil adulterant, induces systemic immunosuppression in Balb/c mice in an oral 28 days repeated dose toxicity study.

Consumption of edible oils contaminated with Argemone oil (AO) leads to a clinical condition called "Epidemic dropsy". Earlier studies have reported that metabolism and oxidative stress primarily contributes to AO toxicity, however, the involvement of immune system has not been assessed so far. Therefore, the present study was undertaken to systematically assess the effect of AO exposure on the function of immune system in Balb/c mice. The repeated exposure of AO for 28 days caused prominent regression of spleen and thymus; severe inflammatory changes in spleen depicted by the loss of distinct follicles, increased megakaryocyte infiltration, and enhanced expression levels of inflammatory markers (iNOS & COX-2). At the functional level, AO exposure significantly abrogated the mixed lymphocyte reaction and mitogen-stimulated lymphoproliferative activity of T and B cells, which is reflective of profound lymphocyte dysfunction upon antigen exposure. In concordance with the loss in functional activity of lymphocytes in AO exposed animals, it was found the AO altered the relative percentage of CD3+, CD4+, and CD28 + T cells. Further, there was a marked decrease in the relative distribution of cells with prominent MHC I and CD1d expression in AO exposed splenocytes. Moreover, reduced levels of immune stimulatory cytokines (TNF-α, IFN-γ, IL-2, IL-4, and IL-6), and increased levels of immunosuppressive cytokine IL-10 were detected in the serum of AO treated mice. Along with T and B cells, AO exposure also affected the phenotype and activation status of macrophages suggesting the inclination towards "alternative activation of macrophages". Altogether, these functional changes in the immune cells are contributing factors in AO induced immunosuppression.

Invariant natural killer T cells: boon or bane in immunity to intracellular bacterial infections?

Invariant natural killer T (iNKT) cells represent a specialized subset of innate lymphocytes that recognize lipid and glycolipid antigens presented to them by nonclassical MHC-I CD1d molecules and are able to rapidly secrete copious amounts of a variety of cytokines. iNKT cells possess the ability to modulate innate as well as adaptive immune responses against various pathogens. Intracellular bacteria are one of the most clinically significant human pathogens that effectively evade the immune system and cause a myriad of diseases of public health concern globally. Emerging evidence suggests that iNKT cells can confer immunity to intracellular bacteria but also inflict pathology in certain cases. We summarize the current knowledge on the contribution of iNKT cells in the host defense against intracellular bacterial infections, with a focus on the underlying mechanisms by which these cells induce protective or pathogenic reactions including the pathways of direct action (acting on infected cells) and indirect action (modulating dendritic, NK and T cells). The rational exploitation of iNKT cells for prophylactic and therapeutic purposes awaits a profound understanding of their functional biology.

Reduced numbers of regulatory B cells are negatively correlated with disease activity in patients with new-onset rheumatoid arthritis.

This study is aimed at determining the numbers of circulating Treg and Breg cells in patients with new-onset rheumatoid arthritis and during subsequent drug therapies. Patients were treated orally with 10 mg methotrexate weekly, and 20 mg leflunomide and 60 mg common threewingnut root daily (Lei Gong Teng) for 12 weeks, but received no steroid therapy. Basal measurements were performed of serum C-reactive protein, anticyclic citrullinated peptide antibody, and erythrocyte sedimentation rate, and the numbers of cluster of differentiation CD4(+)CD25(+)Foxp3(+) T cells, interleukin 10 (IL10)-expressing on CD5(+)CD1d(+) and TIM1(+) B cells. Compared with the healthy controls, patients exhibited significantly less numbers of circulating CD19(+)TIM1(+)IL10(+), CD19(+)CD5(+)CD1d(+)IL10(+) B cells and CD4(+)CD25(+)Foxp3(+) T cells (P < 0.001, all). Drug therapy modulated the balance of different subsets of Breg and Treg cells. The numbers of CD19(+)TIM1(+)IL10(+) and CD19(+)CD5(+)CD1d(+)IL10(+) B cells correlated positively with the numbers of CD4(+)CD25(+)Foxp3(+) T cells in these patients (r = 0.707, P = 0.001; r = 0.481, P = 0.007, respectively). The values of DAS28 were negatively correlated with the numbers of CD19(+)TIM1(+)IL10(+) and CD19(+)CD5(+)CD1d(+)IL10(+) B cells, and CD4(+)CD25(+)Foxp3(+) T cells (r = -0.533, P = 0.023; r = -0.442, P = 0.016; and r = -0.444, P = 0.014, respectively). Of note, TIM1(+) B cells identified more circulating IL10(+) B cells than CD5(+)CD1d(+) B cells. Our data indicate that Breg and Treg cells have a potentially crucial role in controlling disease activity in rheumatoid arthritis patients, and TIM1(+) Breg cells may be a viable therapeutic target for these patients.

Retinoic acid and α-galactosylceramide regulate the expression of costimulatory receptors and transcription factors responsible for B cell activation and differentiation.

Mature naïve B cells possess a number of BCR coreceptors and other antigen receptors, including the MHC class I-like molecule CD1d, but little is known of the response of B cells to stimulation by the CD1d ligand, α-galactosylceramide (αGalCer). Previously, we showed that all-trans-retinoic acid (RA) increases the expression of CD1d and the magnitude of CD1d-mediated antibody production in vivo. Potential mechanisms could include changes in the expression of costimulatory molecules and transcription factors that regulate plasma cell formation. In the present study, we have used isolated purified B cells and in vivo studies to demonstrate that αGalCer and RA initiate a regulated expression of several genes essential for B cell activation and differentiation, such as Pax-5, Blimp-1, IRF-4 and activation-induced cytidine deaminase (Aid). Moreover, whereas αGalCer mainly increased the expression of Pax-5, CD40 and CD86 that are critical for B cell activation, RA predominantly increased CD138⁺ and Fas⁺-PNA⁺ B cells, which represent more advanced B cell differentiation. It is also noteworthy that αGalCer enriched a CD19hi subset of B cells, which represent B cells with more differentiated phenotype and higher potential for antibody production. In vivo, treatment with αGalCer enriched the CD19hi population, which, after sorting, produced more anti-TT IgG by ELISPOT assay. Together, our data demonstrate that RA and αGalCer can regulate B cell activation and differentiation at multiple levels in a complementary manner, facilitating the progress of B cells towards antibody secreting cells.