HSC70 is a novel binding partner involved in the capture of immunoglobulins on B cells in the NOD mouse.

B cells have been shown to be essential for Type 1 diabetes development in the non-obese diabetic mouse, where their contribution as antigen presenting cells has been emphasised. Other important functions for B cells include surface capture of immunoglobulins and transportation of immune complexes, with subsequent endocytosis, antigen processing and antigen presentation. We have previously demonstrated that NOD B cells capture IgM and IgG immune complexes through an unknown surface molecule. In this study, we revealed the presumptive immunoglobulin-binding molecule to be HSC70. Moreover, we detected increased levels of HSC70 on NOD B cells. HSC70 has been shown to play a role in antigen processing and presentation as well as being important in several autoimmune diseases, including rheumatoid arthritis and systemic lupus erythematosus. Due to its protein stabilising properties, increased HSC70 could contribute to enhanced self-antigen collection and presentation and thereby contribute to the development of Type 1 diabetes.

Increased expression of TACI on NOD B cells results in germinal centre reaction anomalies, enhanced plasma cell differentiation and immunoglobulin production.

B cells have an important pathogenic role in the development of type 1 diabetes in the non-obese diabetic (NOD) mouse. We have previously reported that NOD mice display an increased percentage of TACIhigh -expressing B cells compared with C57BL/6 mice and this trait is linked to chromosomes 1 and 8. In this paper the genetic association of the transmembrane activator, calcium modulator and cyclophilin ligand interactor (TACI) trait was confirmed using double congenic NOD.B6C1/Idd22 mice. TACI ligation by a proliferation-inducing ligand (APRIL) has been shown to influence plasma cell differentiation, immunoglobulin production and isotype switch. Hence, the functional consequence of the up-regulation of TACI on NOD B cells was analysed both in vitro and in vivo. NOD B cells stimulated with APRIL showed an enhanced plasma cell differentiation and class switch to IgG and IgA compared with B cells from C57BL/6 mice. Moreover, flow cytometry analyses revealed that germinal centre B cells in NOD failed to down-regulate TACI. Availability of the TACI ligand B-cell activating factor (BAFF) has been shown to be a limiting factor in the germinal centre reaction. In line with this, upon immunization with 4-hydroxy-3-nitrophenylacetyl hapten-conjugated hen egg lysozyme, NOD mice produced higher titres of low-affinity antibodies compared with C57BL/6 mice. This observation was supported by the detection of increased levels of BAFF in NOD germinal centres after immunization compared with C57BL/6 by immunofluorescence. Our results support the hypothesis that increased TACI expression on NOD B cells contributes to the pathogenesis of type 1 diabetes in the NOD mouse.

Noncontaminated dietary oats may hamper normalization of the intestinal immune status in childhood celiac disease.

OBJECTIVES: Life-long, strict gluten-free diet (GFD) is the only treatment for celiac disease (CD). Because there is still uncertainty regarding the safety of oats for CD patients, the aim was to investigate whether dietary oats influence the immune status of their intestinal mucosa. METHODS: Paired small intestinal biopsies, before and after >11 months on a GFD, were collected from children with CD who were enrolled in a randomized, double-blind intervention trial to either of two diets: standard GFD (GFD-std; n=13) and noncontaminated oat-containing GFD (GFD-oats; n=15). Expression levels of mRNAs for 22 different immune effector molecules and tight junction proteins were determined by quantitative reverse transcriptase (RT)-PCR. RESULTS: The number of mRNAs that remained elevated was higher in the GFD-oats group (P=0.05). In particular, mRNAs for the regulatory T cell (Treg) signature molecules interleukin-10 (IL-10) and transforming growth factor-ß1 (TGF-ß1), the cytotoxicity-activating natural killer (NK) receptors KLRC2/NKG2C and KLRC3/NKG2E, and the tight junction protein claudin-4 remained elevated. Between the two groups, most significant differences were seen for claudin-4 (P=0.003) and KLRC3/NKG2E (P=0.04). CONCLUSIONS: A substantial fraction of pediatric CD patients seem to not tolerate oats. In these patients, dietary oats influence the immune status of the intestinal mucosa with an mRNA profile suggesting presence of activated cytotoxic lymphocytes and Tregs and a stressed epithelium with affected tight junctions. Assessment of changes in levels of mRNA for claudin-4 and KLC3/NKG2E from onset to after a year on oats containing GFD shows promise to identify these CD patients.

The prolonged and enhanced immune response in the non-obese diabetic mouse is dependent on genes in the Idd1/24, Idd12 and Idd18 regions.

In non-obese diabetic (NOD) mice B cells are an absolute requirement for T1D development. NOD mice display various B cell related immune deviations when compared to normal mice such as an enhanced and prolonged immune response towards several antigens, including non-self immunoglobulins. We hypothesized that this trait contributes to diabetes pathogenesis, and investigated the genetic factor(s) governing the altered immune response. A (NODxC57BL/6)F(2) cohort (n = 214) were analyzed for its primary immune response against a BALB/c derived monoclonal antibody, and a genome wide linkage analysis was performed. Significant linkage to the Idd1/Idd24, Idd12 and Idd18.1 regions as well as to a proximal region (marker D2Mit367, 33.5 Mb) on chromosome 2 was detected. We verified the observed linkage by analyzing a set of H2 congenic NOD and C57BL/6 mice and narrowed down the region to 8 Mb. Interaction between Idd1/24 and Idd12, as well as the novel locus on chromosome 2 was observed. However, the action by Idd18.1 was not influenced by any of the other loci. In addition to the known H2 I-Aß(g7) allelic variant of Idd1 in NOD, candidate gene analysis revealed a significant difference in the transcription of the H2-O/DO molecule. We hypothesize that multiple mechanisms contribute to the loss of immune response control, including that peptide loading on MHC class II in B cells of NOD is altered.

Enhanced capture of extramembranous IgM and IgG on B cells in the NOD mouse--implications for immune complex trapping.

Binding of various antibody isotypes to B cells through either FcgammaRs or complement receptors has been attributed to play several roles, e.g. in immune complex (IC) transportation and regulation of B cell receptor signaling. We have revealed a novel B cell intrinsic receptor for IgM and IgG which is present in C57BL/6 (B6) mice and is more abundant in non-obese diabetic (NOD) mice. As a consequence, the level of extramembranous IgG monomers and IgM pentamers on peripheral blood B cells from NOD mice was significantly higher compared with B6 mice. The effect of this aberration was that all B cells in peripheral blood of (NOD.IgH(a) x B6(IgH(b)))F(1) mice carried both IgM allotypes on their surface. In addition, analysis of IC binding using IgG- or IgM-opsonized bacterial particles revealed a higher degree of binding in NOD mice compared with B6. We hypothesize that this novel Ig-binding receptor is part of the normal immune system function. The aberrant function in the NOD mouse could contribute to the development of Type 1 diabetes by altering normal B cell functions such as activation, IC transportation and B cell homeostasis.

Idd-linked genetic regulation of TACIhigh expressing B cells in NOD mice.

In NOD mice, B cells play a key role in the initiation of type 1 diabetes pathogenesis. We have identified a novel NOD-specific B cell-related trait, i.e. the increased percentage of TACI(high)-expressing splenic B cells, by comparing NOD mice with non-autoimmune C57BL/6 mice. Using athymic NOD mice, we determined that this trait was T cell independent. We mapped the loci contributing to the increased proportion of TACI(high) expressing splenic B cells and found that the control of TACI expression was strongly linked to chromosome 1, in a region which includes the insulin-dependent diabetes (Idd) 5 loci. Moreover, another locus potentially involved was detected in the vicinity of Idd22 on chromosome 8. Interestingly, when analyzing age-dependent contribution to the obtained LOD scores we observed that the linkage to chromosome 8 was explained solely by mice > or =61 days of age, suggesting a temporal genetic regulation of TACI expression. In addition, analysis of genetic interaction between chromosome 1 and chromosome 8 indicated that the two loci acted in an additive fashion. Our findings corroborate the notion that B cell deviations contribute to type 1 diabetes development, and suggest a temporal regulation of TACI(high) expression, possibly influenced by the ongoing autoimmune process.