Zinc Induces Dendritic Cell Tolerogenic Phenotype and Skews Regulatory T Cell-Th17 Balance.

Zinc (Zn) is an essential metal for development and maintenance of both the innate and adaptive compartments of the immune system. Zn homeostasis impacts maturation of dendritic cells (DCs) that are important in shaping T cell responses. The mechanisms by which Zn regulates the tolerogenic phenotype of DCs remain largely unknown. In this study, we investigated the effect of Zn on DC phenotype and the generation of Foxp3(+) regulatory T cells (Tregs) using a model of Histoplasma capsulatum fungal infection. Exposure of bone marrow-derived DCs to Zn in vitro induced a tolerogenic phenotype by diminishing surface MHC class II (MHCII) and promoting the tolerogenic markers, programmed death-ligand (PD-L)1, PD-L2, and the tryptophan degrading enzyme, IDO. Zn triggered tryptophan degradation by IDO and kynurenine production by DCs and strongly suppressed the proinflammatory response to stimulation by TLR ligands. In vivo, Zn supplementation and subsequent H. capsulatum infection supressed MHCII on DCs, enhanced PD-L1 and PD-L2 expression on MHCII(lo) DCs, and skewed the Treg-Th17 balance in favor of Foxp3(+) Tregs while decreasing Th17 cells. Thus, Zn shapes the tolerogenic potential of DCs in vitro and in vivo and promotes Tregs during fungal infection.

Prevention of autoimmune diabetes and induction of ß-cell proliferation in NOD mice by hyperbaric oxygen therapy.

We evaluated the effects of hyperbaric oxygen therapy (HOT) on autoimmune diabetes development in nonobese diabetic (NOD) mice. Animals received no treatment or daily 60-min HOT 100% oxygen (HOT-100%) at 2.0 atmospheres absolute and were monitored for diabetes onset, insulitis, infiltrating cells, immune cell function, and ß-cell apoptosis and proliferation. Cyclophosphamide-induced diabetes onset was reduced from 85.3% in controls to 48% after HOT-100% (P < 0.005) and paralleled by lower insulitis. Spontaneous diabetes incidence reduced from 85% in controls to 65% in HOT-100% (P = 0.01). Prediabetic mice receiving HOT-100% showed lower insulitis scores, reduced T-cell proliferation upon stimulation in vitro (P < 0.03), increased CD62L expression in T cells (P < 0.04), reduced costimulation markers (CD40, DC80, and CD86), and reduced major histocompatibility complex class II expression in dendritic cells (DCs) (P < 0.025), compared with controls. After autoimmunity was established, HOT was less effective. HOT-100% yielded reduced apoptosis (transferase-mediated dUTP nick-end labeling-positive insulin-positive cells; P < 0.01) and increased proliferation (bromodeoxyuridine incorporation; P < 0.001) of insulin-positive cells compared with controls. HOT reduces autoimmune diabetes incidence in NOD mice via increased resting T cells and reduced activation of DCs with preservation of ß-cell mass resulting from decreased apoptosis and increased proliferation. The safety profile and noninvasiveness makes HOT an appealing adjuvant therapy for diabetes prevention and intervention trials.

A dominant suppressive MHC class II haplotype interacting with autosomal genes controls autoantibody production and chronicity of arthritis.

OBJECTIVE: To investigate the genetic control of chronic arthritis and collagen epitope specific antibody responses in an experimental model for rheumatoid arthritis. METHODS: The chronic collagen induced arthritis (CCIA) model was used, induced with collagen type II (CII) in mineral oil lacking mycobacterium in BALB/c (n=24), B10.Q (n=44), (BALB/c × B10.Q) F1 (n=85) and B10.Q × (BALB/c × B10.Q) N2 (n=684) mice. Genome-wide genotyping for 190 N2 mice was performed with extreme phenotypes: chronic arthritis that persisted for 4 months or non-affected. Statistical and linkage analysis were performed with R/qtl software using arthritis and serum subphenotypes. RESULTS: (BALB/c × B10.Q) F1 mice were highly prone to develop a chronic relapsing arthritis (66%), whereas both parental strains were relatively resistant: BALB/c (H-2(d); 0%) and B10.Q (H-2(q); 4.5%). CCIA experiments were performed on 684 mice backcrossed to B10.Q; 38% of the mice developed arthritis and more than half of them developed chronic arthritis phenotype. Genome-wide genotyping revealed mainly the major histocompatibility complex (MHC) locus that had an independent and dominant influence on the chronicity. Interestingly, the H2(d) allele had a dominant suppressive effect. This effect overrode the role of other loci as interaction analysis, after conditioning MHC, revealed additional loci, controlling arthritis and autoantibody phenotypes. CONCLUSIONS: A dominant negative influence of specific MHC haplotype (H2(d)) on CCIA was identified. Further, loci controlling the autoantibody response to different CII epitopes were also identified, and it has been shown that these are dependent on MHC and non-MHC genes.

A phase I pharmacokinetic and biological correlative study of IMP321, a novel MHC class II agonist, in patients with advanced renal cell carcinoma.

PURPOSE: To evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics of IMP321, a recombinant soluble LAG-3Ig fusion protein which agonizes MHC class II-driven dendritic cell activation. EXPERIMENTAL DESIGN: Patients with advanced renal cell carcinoma were treated with escalating doses of IMP321 s.c. Blood samples were assayed to determine plasma pharmacokinetic parameters, detect human anti-IMP321 antibody formation, and determine long-lived CD8 T cell responses. RESULTS: Twenty-one advanced renal cell carcinoma patients received 119 injections of IMP321 at doses ranging from 0.050 to 30 mg/injection s.c. biweekly for 6 injections. No clinically significant adverse events were observed. Good systemic exposure to the product was obtained following s.c. injections of doses above 6 mg. IMP321 induced both sustained CD8 T-cell activation and an increase in the percentage of long-lived effector-memory CD8 T cells in all patients at doses above 6 mg. Tumor growth was reduced and progression-free survival was better in those patients receiving higher doses (>6 mg) of IMP321: 7 of 8 evaluable patients treated at the higher doses experienced stable disease at 3 months compared with only 3 of 11 in the lower dose group (P = 0.015). CONCLUSION: The absence of toxicity and the demonstration of activity at doses above 6 mg warrant further disease-directed studies of IMP321 in combined regimens (e.g., chemoimmunotherapy).

Clinical link between MHC class II haplotype and interferon-beta (IFN-beta) immunogenicity.

Interferon-beta (IFN-beta) is currently the first-line therapy for the treatment of multiple sclerosis (MS). However, a significant percentage of MS patients develop anti-IFN-beta antibodies, which can reduce the efficacy of the drug. We describe an association between a common MHC class II allele (DRB1*0701), present in 23% of the patients studied, and the anti-IFN-beta antibody response. We identified IFN-beta epitopes using a peptide-binding assay with B cell lines expressing this allele. Moreover, epitope-specific activation responses obtained with peripheral blood mononuclear cells (PBMCs) from IFN-beta treated patients with the DRB1*0701 allele indicated a role for T-cell activation in IFN-beta immunogenicity. These results suggest that HLA typing of MS patients may provide an accurate screen for subjects who are likely to develop anti-IFN-beta antibodies and should therefore be considered for alternative therapies. In addition, elucidation of the factors underlying the anti-IFN-beta antibody response should accelerate the engineering of less immunogenic IFN-beta therapeutics.

Mechanism of action of donor-specific transfusion in inducing tolerance: role of donor MHC molecules, donor co-stimulatory molecules, and indirect antigen presentation.

Donor-specific transfusion (DST) can synergize with T cell co-stimulatory blockade in inducing tolerance in several transplant models, but the mechanism of action of DST is poorly characterized. This study used genetically altered mice in an established model of cardiac transplantation to study the role of MHC and co-stimulatory molecule expression on DST cells in mediating the immunomodulatory effects of DST. In addition, to examine the role of indirect antigen presentation in the effect of DST, experiments used recipient mice that do not express MHC class II molecules on peripheral antigen-presenting cells, but do have functional CD4(+) T cells (II(-)4(+)). As previously reported, treatment with DST from wild-type donors in combination with CD154 blockade induced tolerance in wild-type recipients of cardiac allografts. Tolerance in this model is also induced despite the absence of MHC class I and II, CD40, or B7 molecules on transfused cells. In contrast, eliminating the indirect pathway using II(-)4(+) recipients blocked the induction of long-term cardiac allograft survival by DST. These results indicate that the indirect antigen recognition pathway mediates the immunomodulatory effect of DST in inducing transplantation tolerance in vivo.

n-3 polyunsaturated fatty acids inhibit the antigen-presenting function of human monocytes.

Diets rich in n-3 polyunsaturated fatty acids (PUFAs) are associated with suppression of cell-mediated immune responses, but the mechanisms are unclear. We hypothesized that n-3 PUFAs can inhibit the function of human antigen-presenting cells. A prerequisite for this role of blood monocytes is the cell surface expression of major histocompatibility complex (MHC) class II molecules [human leukocyte antigen (HLA)-DR, -DP, and -DQ], aided by the presence of intercellular adhesion molecule-1 (ICAM-1) and leukocyte function associated antigens 1 and 3. We showed previously that the n-3 PUFA eicosapentaenoic acid (EPA) inhibits the expression of HLA-DR on unstimulated human monocytes in vitro, but that docosahexaenoic acid (DHA) enhances its expression. However, both n-3 PUFAs suppress the expression of HLA-DR, HLA-DP, and ICAM-1 on interferon-gamma-activated monocytes. We also established that dietary fish-oil supplementation can inhibit the expression of these surface molecules on circulating human monocytes. We subsequently showed that when EPA and DHA were combined in the same ratio as is commonly found in fish-oil-supplement capsules (3:2), there was no significant effect in vitro on the expression of HLA-DR on unstimulated monocytes, but the expression on activated monocytes remained significantly inhibited. In the same in vitro system, the ability of activated monocytes to present antigen to autologous lymphocytes was significantly reduced after culture with the combined n-3 PUFAs. These findings provide one potential mechanism for the beneficial effect of fish oil in the treatment of rheumatoid arthritis, a disorder associated with elevated expression of MHC class II and adhesion molecules on monocytes present within affected joints.