A recombination event in the 5′ flanking region of the Ly-6C gene correlates with impaired expression in the NOD, NZB and ST strains of mice

Circulating platelet-neutrophil aggregates characterize the development of type 1 diabetes in humans and NOD mice

Platelet-neutrophil aggregates (PNAs) facilitate neutrophil activation and migration and could underpin the recruitment of neutrophils to the pancreas during type 1 diabetes (T1D) pathogenesis. PNAs, measured by flow cytometry, were significantly elevated in the circulation of autoantibody-positive (Aab⁺) children and new-onset T1D children, as well as in pre-T1D (at 4 weeks and 10–12 weeks) and T1D-onset NOD mice, compared with relevant controls, and PNAs were characterized by activated P-selectin⁺ platelets. PNAs were similarly increased in pre-T1D and T1D-onset NOD isolated islets/insulitis, and immunofluorescence staining revealed increased islet-associated neutrophil extracellular trap (NET) products (myeloperoxidase [MPO] and citrullinated histones [CitH3]) in NOD pancreata. In vitro, cell-free histones and NETs induced islet cell damage, which was prevented by the small polyanionic drug methyl cellobiose sulfate (mCBS) that binds to histones and neutralizes their pathological effects. Elevated circulating PNAs could, therefore, act as an innate immune and pathogenic biomarker of T1D autoimmunity. Platelet hyperreactivity within PNAs appears to represent a previously unrecognized hematological abnormality that precedes T1D onset. In summary, PNAs could contribute to the pathogenesis of T1D and potentially function as a pre-T1D diagnostic.

Postnatal Hematopoiesis and Gut Microbiota in NOD Mice Deviate from C57BL/6 Mice

Neonatal studies in different mouse strains reveal that early life colonization affects the development of adaptive immunity in mice. The nonobese diabetic (NOD) mouse spontaneously develops autoimmune diabetes, but neonatal studies of NOD mice are lacking. We hypothesized that NOD mice deviate from another much used mouse strain, C57BL/6, with respect to postnatal microbiota and/or hematopoiesis and compared this in newborn mice of dams housed under the same conditions. A distinct bacteria profile rich in staphylococci was found at postnatal days (PND) 1-4 in NOD mice. Furthermore, a distinct splenic cell profile high in a granulocytic phenotype was evident in the neonatal NOD mice whereas neonatal C57BL/6 mice showed a profile rich in monocytes. Neonatal expression of Reg3g and Muc2 in the gut was deviating in NOD mice and coincided with fewer bacteria attaching to the Mucosal surface in NOD compared to C57BL/6 mice.

Flow cytometric gating for spleen monocyte and DC subsets: differences in autoimmune NOD mice and with acute inflammation

The role of antigen presenting cells (APCs) in the pathogenesis of autoimmune and other inflammatory diseases is now better understood due to advances in multicolor flow cytometry, gene expression analysis of APC populations, and functional correlation of mouse to human APC populations. A simple but informative nomenclature of conventional and plasmacytoid dendritic cell subsets (cDC1, cDC2, pDC) and monocyte-derived populations incorporates these advances, but accurate subset identification is critical. Ambiguous gating schemes and alterations of cell surface markers in inflammatory condition can make comparing results between studies difficult. Both acute inflammation, such as TLR-ligand stimulation, and chronic inflammation as found in mouse models of autoimmunity can alter DC subset gating. Here, we address these issues using in vivo CpG stimulation as an example of acute inflammation and the non-obese diabetic (NOD) mouse as a model of chronic inflammation.We provide a flow cytometric antibody panel and gating scheme that differentiate 2 monocytic and 3DC subsets in the spleen both at steady state and after CpG stimulation. Using this method, we observed differences in the composition of NOD DCs that have been previously reported, and newly identified increases in the number of NOD monocyte-derived DCs. Finally, we established a protocol for DC phosphoflow to measure the phosphorylation state of intracellular proteins, and use it to confirm functional differences in the identified subsets. Therefore, we present optimized methods for distinguishing monocytic and DC populations with and without inflammation and/or autoimmunity associated with NOD mice.

Redundant Function of Plasmacytoid and Conventional Dendritic Cells Is Required To Survive a Natural Virus Infection

Viruses that spread systemically from a peripheral site of infection cause morbidity and mortality in the human population. Innate myeloid cells, including monocytes, macrophages, monocyte-derived dendritic cells (mo-DC), and dendritic cells (DC), respond early during viral infection to control viral replication, reducing virus spread from the peripheral site. Ectromelia virus (ECTV), an orthopoxvirus that naturally infects the mouse, spreads systemically from the peripheral site of infection and results in death of susceptible mice. While phagocytic cells have a requisite role in the response to ECTV, the requirement for individual myeloid cell populations during acute immune responses to peripheral viral infection is unclear. In this study, a variety of myeloid-specific depletion methods were used to dissect the roles of individual myeloid cell subsets in the survival of ECTV infection. We showed that DC are the primary producers of type I interferons (T1-IFN), requisite cytokines for survival, following ECTV infection. DC, but not macrophages, monocytes, or granulocytes, were required for control of the virus and survival of mice following ECTV infection. Depletion of either plasmacytoid DC (pDC) alone or the lymphoid-resident DC subset (CD8α(+) DC) alone did not confer lethal susceptibility to ECTV. However, the function of at least one of the pDC or CD8α(+) DC subsets is required for survival of ECTV infection, as mice depleted of both populations were susceptible to ECTV challenge. The presence of at least one of these DC subsets is sufficient for cytokine production that reduces ECTV replication and virus spread, facilitating survival following infection.

IMPORTANCE

Prior to the eradication of variola virus, the orthopoxvirus that causes smallpox, one-third of infected people succumbed to the disease. Following successful eradication of smallpox, vaccination rates with the smallpox vaccine have significantly dropped. There is now an increasing incidence of zoonotic orthopoxvirus infections for which there are no effective treatments. Moreover, the safety of the smallpox vaccine is of great concern, as complications may arise, resulting in morbidity. Like many viruses that cause significant human diseases, orthopoxviruses spread from a peripheral site of infection to become systemic. This study elucidates the early requirement for innate immune cells in controlling a peripheral infection with ECTV, the causative agent of mousepox. We report that there is redundancy in the function of two innate immune cell subsets in controlling virus spread early during infection. The viral control mediated by these cell subsets presents a potential target for therapies and rational vaccine design.

Abnormalities of dendritic cell precursors in the pancreas of the NOD mouse model of diabetes

The non-obese diabetic (NOD) mouse is a widely used animal model for the study of human diabetes. Before the start of lymphocytic insulitis, DC accumulation around islets of Langerhans is a hallmark for autoimmune diabetes development in this model. Previous experiments indicated that an inflammatory influx of these DCs in the pancreas is less plausible. Here, we investigated whether the pancreas contains DC precursors and whether these precursors contribute to DC accumulation in the NOD pancreas. Fetal pancreases of NOD and control mice were isolated followed by FACS using ER-MP58, Ly6G, CD11b and Ly6C. Sorted fetal pancreatic ER-MP58(+) cells were cultured with GM-CSF and tested for DC markers and antigen processing. CFSE labeling and Ki-67 staining were used to determine cell proliferation in cultures and tissues. Ly6C(hi) and Ly6C(low) precursors were present in fetal pancreases of NOD and control mice. These precursors developed into CD11c(+) MHCII(+) CD86(+) DCs capable of processing DQ-OVA. ER-MP58(+) cells in the embryonic and pre-diabetic NOD pancreas had a higher proliferation capacity. Our observations support a novel concept that pre-diabetic DC accumulation in the NOD pancreas is due to aberrant enhanced proliferation of local precursors, rather than to aberrant "inflammatory infiltration" from the circulation.

Dynamic control of self-specific CD8+ T cell responses via a combination of signals mediated by dendritic cells

It is acknowledged that T cell interactions with mature dendritic cells (DC) lead to immunity, whereas interactions with immature DC lead to tolerance induction. Using a transgenic murine system, we have examined how DC expressing self-peptides control naive, self-reactive CD8+ T cell responses in vitro and in vivo. We have shown, for the first time, that immature DC can also stimulate productive activation of naive self-specific CD8+ T cells, which results in extensive proliferation, the expression of a highly activated cell surface phenotype, and differentiation into autoimmune CTL. Conversely, mature DC can induce abortive activation of naive CD8+ T cells, which is characterized by low-level proliferation, the expression of a partially activated cell surface phenotype which does not result in autoimmune CTL. Critically, both CD8+ T cell responses are determined by a combination of signals mediated by the DC, and that altering any one of these signals dramatically shifts the balance between autoimmunity and self-tolerance induction. We hypothesize that DC maintain the steady state of self-tolerance among self-specific CD8+ T cells in an active and dynamic manner, licensing productive immune responses against self-tissues only when required.

Pathogenic T-cell clones in autoimmune diabetes: more lessons from the NOD mouse

T-cell clones that can efficiently transfer diabetes to prediabetic nonobese diabetic (NOD) mice provide a powerful approach to dissecting the autoimmune disease process and for investigating immunoregulation. Diabetogenic T-cell clones carried in culture allow for detailed analysis of T-cell effector function and in vivo activity, and thus the contribution of a single clonotype to pathogenesis can be studied. As T cells comprising most or all of the repertoire in T-cell receptor transgenic (TCR-Tg) mice, diabetogenic T-cell clones have led to new variations on the NOD mouse model of autoimmune disease. T-cell clones are being used to screen peptide libraries and proteomic arrays to identify the autoantigens that drive these clones in vivo and to extend our knowledge of the processes that give rise to these antigens. With the identification of peptide agonists and natural ligands, the development of MHC-peptide multimers has been possible. These reagents can track T cells in vivo and thus provide new approaches for disease diagnosis and therapy as well as a versatile set of tools for basic research on how T cells contribute to autoimmune disease.

Ly-6 superfamily members Ly-6A/E, Ly-6C, and Ly-6I recognize two potential ligands expressed by B lymphocytes

Most hemopoietic cells express one or more members of the Ly-6 supergene family of small glycosylphosphatidylinositol-linked proteins. Although levels of Ly-6 proteins vary with stages of differentiation and activation, their function largely remains unknown. To ascertain whether ligands for Ly-6 proteins exist, chimeric proteins were constructed in which Ly-6E, Ly-6C, and Ly-6I were fused to the murine IgM heavy chain. These chimeras specifically stained both developing and mature B lymphocytes, as assessed by flow cytometry. Analysis of variants of the CH27 B cell lymphoma revealed that Ly-6A/E and Ly-6I recognized different molecules. CH27 cells with low levels of Ly-6A/E ligand activity also lost expression of CD22, and cells transfected with CD22 gained the ability to bind the Ly-6A/E chimera and, to a lesser extent, the Ly-6C and Ly-6I chimeric proteins. As many mature B cells coexpress Ly-6A/E and CD22, the function of Ly-6 molecules may be to associate with other membrane proteins, possibly concentrating these ligands in lipid rafts, rather than acting directly as cell:cell adhesion molecules.

Ly-6I, a new member of the murine Ly-6 superfamily with a distinct pattern of expression

A new member of the mouse Ly-6SF, designated Ly-6I, has been isolated as a gene homologous to a segment of the Ly-6C gene. A single allelic difference in the mature protein sequence was identified, which is similar to other Ly-6SF members. Ly-6I mRNA has been detected in a wide range of tissues and cell lines, and a rabbit polyclonal Ab has been used to determine that Ly-6I protein is present at a low constitutive level on cell lines from several different lineages. In contrast to Ly-6C and Ly-6A/E, the Ly-6I gene is only weakly responsive to IFNs. Expression in vivo is most abundant on bone marrow populations and is coexpressed with Ly-6C on granulocytes and macrophages. However, Ly-6I is also expressed on immature B cell populations that do not express Ly-6C. Expression on mature B cells in spleen is uniformly low. Similarly, Ly-6I is expressed on TCRlow/int, but not TCRhigh, thymocytes. Ly-6I is re-expressed on Ly-6Chigh T cells in the periphery. Thus, Ly-6I may be a useful marker to define maturation stages of both T and B lymphocytes as well as subsets of monocytes and granulocytes.

A T cell activation antigen, Ly6C, induced on CD4+ Th1 cells mediates an inhibitory signal for secretion of IL-2 and proliferation in peripheral immune responses

A T cell activation antigen, Ly6C, is considered to be involved in the autoimmunity of some autoimmune-prone mice; however, the function of Ly6C remains largely unknown. We prepared a rat anti-mouse Ly6C monoclonal antibody (mAb) (S14) that inhibits the proliferation of peripheral T cells stimulated with anti-CD3 mAb in vitro. S14 mAb, the specificity of which is confirmed by a cDNA transfectant, recognizes Ly6C antigen preferentially expressed on a part of CD8+ T cells in peripheral lymphoid organs. The immunohistochemical analysis demonstrates that Ly6C appears on CD8+ T cells in the conventional T cell-associated area of BALB/c but not of nonobese diabetic (NOD) mice, confirming the absence of Ly6C+ T cells in NOD mice. Addition of soluble S14 mAb to the culture does not influence the proliferation of T cells in vitro; however, the S14 mAb coated on the plate clearly inhibits the proliferation and IL-2 production of anti-CD3-stimulated peripheral T cells. The T cells are arrested at the transitional stage from G0/G1 to S+G2/M phases, but they are not induced to undergo apoptotic changes in vitro. This inhibitory signal provided through the Ly6C molecule inhibited IL-2 secretion in a subpopulation of the activated CD4+ T cells. Ly6C is expressed on T cell clones of both Th1 and Th2 cells, but the cytokine secretion from Th1 clones is preferentially inhibited. These results suggest that Ly6C mediates an inhibitory signal for secretion of cytokines from Th1 CD4+ T cells, potentially causing the inhibition of immune response in peripheral lymphoid tissues.

Genetic control of diabetes progression

Autoimmune diabetes in both the human and the nonobese diabetic mouse has elaborate genetics; in the latter case, the disease is influenced by at least 15-20 loci. We anticipated that the genetics would be simpler in the BDC2.5 T cell receptor transgenic mouse model of diabetes, wherein many T cells express a particular diabetogenic specificity. Initiation of insulitis in this model was the same on the two genetic backgrounds analyzed, but the kinetics and penetrance of diabetes were strikingly different, permitting us to focus on genetic influences during a defined window of disease progression. The differences correlated with variations in five genomic intervals, certain ones of which have been previously implicated in susceptibility to autoimmune disease. This reductionist approach indeed simplified the analysis of diabetes susceptibility loci.

Ly-6C regulates endothelial adhesion and homing of CD8(+) T cells by activating integrin-dependent adhesion pathways

Ly-6C belongs to the Ly-6 family of glycosyl phosphatidylinositol-anchored surface glycoproteins and is expressed on a subset of mature CD8(+) T cells. Ly-6C ligation can mediate T cell activation and causes interleukin 2 secretion in cytolytic T cell clones. We characterize herein a new mAb 1G7.G10 against Ly-6C that recognizes an epitope involved in lymphocyte adhesion and in lymphocyte homing. Pretreatment of lymph node lymphocytes and of purified CD8(+) T cells (but not of lymphocytes depleted of CD8(+) T cells) with 1G7.G10 reduced their in vitro binding to lymph node high endothelial venules by 28% and 34%, respectively. This effect was bypassed by cross-linking Ly-6C molecules with 1G7.G10 and a second-step antibody. The in vivo homing of (donor) CD8(+) T lymphocytes to lymph nodes was reduced by Ly-6C blocking with 1G7. G10 (whole antibody) or with its fragments [F(ab) or F(ab)2] by 20% or by 32% and 48%, respectively. Cross-linking of Ly-6C in vitro induced very late antigen-4 and lymphocyte function-associated antigen 1-mediated aggregation of CD8(+) T cells, suggesting that ligand binding to Ly-6C leads to activation of integrins. This activation may facilitate homing of Ly-6C+ CD8(+) T cells in vivo.

Early quantitative and functional deficiency of NK1+-like thymocytes in the NOD mouse

An immunoregulatory role has recently been attributed to the discrete subset of major histocompatibility complex class I-restricted NK1+ mature heat-stable antigen- (HSA-) thymocytes expressing an unusual Vbeta8-biased T cell receptor repertoire. NK1+ T cells are the main interleukin (IL)-4 producers upon priming. We have studied the size and the function of this subset in the nonobese diabetic (NOD) mouse, a model of spontaneous T cell-mediated autoimmune insulin-dependent diabetes. This study was complicated by the absence in this strain of the NK1.1 allele, the only one for which an antibody is available. To circumvent this difficulty, the cells, hereafter designated the NK1+-like T subset, were characterized by the use of monoclonal antibodies which showed the Vbeta8 bias in the CD44+ Ly-49+ MEL-14- 3G11- thymocyte subset of non-autoimmune strains and of its absence in class I-deficient (beta2-microglobulin-/-) mice. A clear deficit in the number of NK1+-like cells was evidenced at 3 weeks of age in NOD mice. It was still present at 8 weeks of age in the double-negative CD4-CD8- population. The functional anomaly was even more striking: NOD mouse NK1+-like thymocytes virtually lacked the ability to produce IL-4 at 3 weeks and still showed a very reduced capacity at 8 weeks. NK1+ T cell deficiency was also suggested in the periphery by the reduction of Ly-49A+ cells in the spleen of 3- and 8-week-old NOD mice and the absence of short-term production of IL-4 in vitro by NOD mouse spleen cells 90 min after the administration of anti-CD3 antibody, a response attributed to NK1+ T cells. Taken together, these data demonstrate a very early defect in NK1+-like T cells which could be involved in the genesis of autoimmunity in NOD mice through a deficiency in Th2 cell function.

Genetic polymorphisms of the non-obese diabetic (NOD) mouse

The non-obese diabetic (NOD) mouse is a polygenic model of insulin-dependent diabetes. To better understand the biology, immunology and genetics of this mouse strain NOD mice were typed for RFLP at 29 loci and microsatellite variation at a further nine loci. Mice were also typed for the expression of lymphocyte differentiation antigens. Comparisons were made with two non-diabetic strains, C57BL/6 and SJL, for these markers. A number of restriction fragment length polymorphisms (RFLP) were defined: seven between C57BL/6 and NOD; five between SJL and NOD; and four in which both C57BL/6 and SJL differed from NOD. Previously reported microsatellite results were extended by defining the SJL alleles at these loci, finding five loci at which NOD differed from B6 alone, and four loci at which NOD differed from both B6 and SJL. In addition, the NOD Igh allotype and alleles for a number of lymphocyte differentiation antigens were defined for the first time. The expression of uncommon alleles of these antigens suggests candidates whose role in the diabetogenic process can be tested.

Type 1 diabetes mellitus: an imbalance between effector and regulatory T cells?

Abundant evidence now exists that autoimmunity plays a critical role in the pathogenesis of type 1 (insulin-dependent) diabetes mellitus. The non-obese diabetic (NOD) mouse is an extensively studied animal model of this T-cell-mediated autoimmune disease. Our laboratory has focused on isolating diabetogenic T cell clones from NOD mice as a means of elucidating the pathogenesis of type 1 diabetes. This experimental approach presupposes that type 1 diabetes in NOD mice results from the action of islet-reactive T cells that are not present in other mouse strains; the diabetogenic T cells would therefore represent "forbidden clones" which exist in NOD mice as a result of a failure of clonal deletion. While the inappropriate presence of diabetogenic T cells probably plays a central role in murine diabetes, it cannot explain all aspects of the disease. Type 1 diabetes is a chronic disorder with a lengthy preclinical stage; if the diabetogenic T cells acted in an unopposed fashion, one might expect to see a much more fulminant clinical course. This observation suggests that regulatory influences are likely to exist in this disease--a possibility supported by recent experimental data. If these regulatory influences could be identified and enhanced, specific immunotherapy for type 1 diabetes could be achieved.

Genetic analysis of autoimmune type 1 diabetes mellitus in mice

Two genes, Idd-3 and Idd-4, that influence the onset of autoimmune type 1 diabetes in the nonobese diabetic mouse have been located on chromosomes 3 and 11, outside the chromosome 17 major histocompatibility complex. A genetic map of the mouse genome, analysed using the polymerase chain reaction, has been assembled specifically for the study. On the basis of comparative maps of the mouse and human genomes, the homologue of Idd-3 may reside on human chromosomes 1 or 4 and Idd-4 on chromosome 17.

Mosaicism of tyrosinase-locus transcription and chromatin structure in dark vs. light melanocyte clones of homozygous chinchilla-mottled mice

The chinchilla-mottled (cm) mutation at the mouse tyrosinase-encoding locus leads to a transversely striped pattern of dark- and light-grey coat colors in homozygotes. The same basic pattern occurs in various other genotypes and has previously been found to represent the clonal developmental history of melanocytes. In a homozygote such as cm/cm, cis-acting mechanisms would be expected to account for the color differences. To search for these mechanisms, the genomic structure of the mutation was examined and compared with the wild-type, and its function was compared in cultured melanocyte clones of the respective colors. Evidence from restriction mapping indicated that the coding region of the mutant gene resembles that of the fully and uniformly pigmented wild-type. However, the upstream sequences are rearranged in the mutation. The rearrangement begins 5 kb 5' of the transcription initiation site and is estimated to encompass at least 30 kb of distal upstream sequence. At least two stable functional states of the cm gene were detectable: Light-cell clones have low levels of tyrosinase-specific transcription, reduced DNAase I sensitivity of tyrosinase chromatin, and no detectable hypersensitive sites near the gene; dark-cell clones have higher (but subnormal) levels of transcription, greater sensitivity of chromatin to DNAase I, and a hypersensitive site in the promoter region. The changed relation between the structural gene and its upstream region may separate it from cis-acting control elements, resulting in reduced and variable ability to achieve the appropriate chromatin configuration near the time of melanocyte determination; differences in expression among clonal initiator cells are then mitotically perpetuated.