oBJective: In NOD.H2 h4 mice, high dietary iodine intake has been known to cause Iodineaccelerated spontaneous Autoimmune thyroiditis (IsAt) via an unknown mechanism. the aim of the study was to examine whether the NOD.H2 h4 genetic background predisposes to enhanced iodine organification in thyroglobulin (tg), a target autoantigen in IsAt. DEsIGN: to avoid issues associated with an ongoing anti-tg antibody response, we assessed tg iodination levels in iodine-fed, b-cell deficient NOD.H2 h4 mice. Additionally, we tested whether humoral or cellular immune responses of iodine-fed NOD.H2 h4 mice are preferentially directed to tg with increased iodine content (I-tg) or known pathogenic tg peptides that contained iodine. rEsULts: the iodine content of tg was not significantly different between control (9.0±2.7 I atoms per monomer) and iodine-fed mice (10.9±0.3 I atoms per monomer). Furthermore, in iodine-fed NOD.H2 h4 mice developing IsAt, strong but equivalent serum IgG responses were detected to both tg or I-tg, whereas their lymphoid cells were stimulated weakly but equally well by tg or I-tg in vitro and did not show reactivity against a panel of five pathogenic tg peptides that contained iodine. cONcLUsIONs: the results suggest that development of IsAt in NOD.H2 h4 mice is not associated with enhanced iodine organification or differential b-or t-cell responses to iodinated determinants in tg.

In the field of autoimmune thyroiditis, NOD.H2(h4) mice have attracted significant and increasing attention since they not only develop spontaneous disease but they present thyroiditis with accelerated incidence and severity if they ingest iodide through their drinking water. This animal model highlights the interplay between genetic and dietary factors in the triggering of autoimmune disease and offers new opportunities to study immunoregulatory parameters influenced by both genes and environment. Here, we review experimental findings with this mouse model of thyroiditis.

Background: Enhanced iodide intake in NOD.H2 h4 mice accelerates the incidence and severity of spontaneous autoimmune thyroiditis (SAT) via an unknown mechanism. A plausible hypothesis is that iodide-induced apoptosis of thyrocytes can create imbalances in antigenic load and/or disruption of immunoregulatory mechanisms that facilitate activation of autoreactive T cells in cervical lymph nodes draining the thyroid. Methods: We examined whether NOD.H2 h4 thyrocytes, exposed to low NaI concentrations in vitro, are more susceptible to apoptosis compared to thyrocytes from CBA/J mice, which are resistant to iodide-accelerated SAT (ISAT). We also looked, at the transcriptional level, for differential activation of genes involved in apoptosis or oxidative stress pathways that may account for potential differences in iodide-mediated apoptosis between NOD.H2 h4 and CBA/J thyrocytes. Results: We report that NOD.H2 h4 thyrocytes, cultured for 24 h at very low (4-8 lM) concentrations of NaI, exhibit high levels (40-55%) of apoptosis, as assessed microscopically following staining with fluorescent caspase inhibitors. Similar treatment of thyrocytes from CBA/J mice, which are resistant to ISAT, yielded significantly lower (10-20%) apoptotic rates. Expression analysis by real-time polymerase chain reaction using arrays of apoptosis-and oxidative stress-related genes showed that NaI intake upregulates the expression of 22 genes involved in ROS metabolism and/or antioxidant function in CBA/J thyrocytes, whereas only two of these genes were upregulated in NOD.H2 h4 thyrocytes. Among the set of overexpressed genes were those encoding thyroid peroxidase (Tpo; 5.77-fold), glutathione peroxidases (Gpx2, Gpx4, Gpx7; 2.03-3.14-fold), peroxiredoxins (Prdx1, Prdx2, Prdx5; 2.27-2.97-fold), superoxide dismutase 1 (Sod1; 3.57-fold), thioredoxin 1 (Txn1; 2.13-fold), and the uncoupling proteins 2 and 3 (Ucp2, Ucp3; 2.01-2.15-fold).Conclusions: The results demonstrate that an impaired control of oxidative stress mechanisms is associated with the observed high susceptibility of NOD.H2 h4 thyrocytes to NaI-mediated apoptosis, and suggest a contributing factor for the development of ISAT in this strain.

Summary Splenic Ly6C high monocytes are innate immune cells involved in the regulation of central nervous system-related diseases. Recent studies have reported the shaping of peripheral immune responses by the gut microbiome via mostly unexplored pathways. In this study, we report that a 4-day antibiotic treatment eliminates certain families of the Bacteroidetes, Firmicutes, Tenericutes, and Actinobacteria phyla in the gut and reduces the levels of multiple pattern recognition receptor (PRR) ligands in the serum. Reduction of PRR ligands was associated with reduced numbers and perturbed function of splenic Ly6C high monocytes, which acquired an immature phenotype producing decreased levels of inflammatory cytokines and exhibiting increased phagocytic and anti-microbial abilities. Addition of PRR ligands in antibiotic-treated mice restored the number and functions of splenic Ly6C high monocytes. Our data identify circulating PRR ligands as critical regulators of the splenic Ly6C high monocyte behavior and suggest possible intervention pathways to manipulate this crucial immune cell subset.