Mice carrying a knock-in mutation of Aicda resulting in a defect in somatic hypermutation have impaired gut homeostasis and compromised mucosal defense.

To elucidate the specific role of somatic hypermutation (SHM) in mucosal immunity, we generated mice carrying a knock-in point mutation in Aicda, which encodes activation-induced cytidine deaminase (AID), an enzyme essential to SHM and class-switch recombination (CSR). These mutant AID(G23S) mice had much less SHM but had normal amounts of immunoglobulin in both serum and intestinal secretions. AID(G23S) mice developed hyperplasia of germinal center B cells in gut-associated lymphoid tissues, accompanied by expansion of microflora in the small intestine. Moreover, AID(G23S) mice had more translocation of Yersinia enterocolitica into mesenteric lymph nodes and were more susceptible than wild-type mice to oral challenge with cholera toxin. Together our results indicate that SHM is critical in maintaining intestinal homeostasis and efficient mucosal defense.

Foxp3(+) T cells regulate immunoglobulin a selection and facilitate diversification of bacterial species responsible for immune homeostasis.

Foxp3(+) T cells play a critical role for the maintenance of immune tolerance. Here we show that in mice, Foxp3(+) T cells contributed to diversification of gut microbiota, particularly of species belonging to Firmicutes. The control of indigenous bacteria by Foxp3(+) T cells involved regulatory functions both outside and inside germinal centers (GCs), consisting of suppression of inflammation and regulation of immunoglobulin A (IgA) selection in Peyer's patches, respectively. Diversified and selected IgAs contributed to maintenance of diversified and balanced microbiota, which in turn facilitated the expansion of Foxp3(+) T cells, induction of GCs, and IgA responses in the gut through a symbiotic regulatory loop. Thus, the adaptive immune system, through cellular and molecular components that are required for immune tolerance and through the diversification as well as selection of antibody repertoire, mediates host-microbial symbiosis by controlling the richness and balance of bacterial communities required for homeostasis.

[High prevalence of secondary hyperparathyroidism due to vitamin D insufficiency in Graves' disease].

We studied concentrations of serum calcium, intact parathyroid hormone (iPTH), and 25 hydroxyvitamin D (25 [OH] D) in 343 patients with Graves' disease (273 women, 70 men) during one year period. The serum 25 (OH) D levels were 37+/-19 nmol/L and vitamin D deficiency (defined as a serum 25 (OH) D value below 25 nmol/L) was found in 35% of the patients. There was a significant seasonal variation in the 25 (OH) D concentrations, with high values of 51+/-21 nmol/L during the summer term (July-September), and with low values of 26+/-17 nmol/L during the winter term (January-March). The average serum iPTH level was 48+/-26 pg/mL, with 26% (89/343) having values above the normal range. Our results showed high prevalence of secondary hyperparathyroidism in patients with Graves' disease during antithyroid drug therapy and vitamin D and/or calcium supplements are recommended for patients with vitamin D deficiency.

Primary thyroid lymphoma associated with Graves' disease.

We report herein a case of thyroid mucosa-associated lymphoid tissue (MALT) lymphoma in a patient receiving antithyroid drug therapy for Graves' disease. A 75-year-old woman first presented with finger tremor and was diagnosed with Graves' disease on the basis of clinical and laboratory findings. Three years later, she presented with rapid and painless enlargement of the thyroid. Ultrasonography revealed a circumscribed hypoechoic area bilaterally in each lobe of the thyroid, and fine-needle aspiration biopsy showed diffuse monotonous infiltration of small- to medium-sized atypical lymphoid cells. (67)Ga scintigraphy was positive exclusively in the thyroid. After total thyroidectomy, the patient received radiation therapy for treatment of stage IE primary thyroid lymphoma. Results of histological examination, immunohistochemical analysis, and flow cytometric analysis confirmed MALT lymphoma. To our knowledge, there have been few published reports of primary thyroid lymphoma associated with Graves' disease. Our experience with this case, though rare, indicates that an enlarged thyroid in cases of Graves' disease should be examined carefully for primary thyroid lymphoma.

The inhibitory receptor PD-1 regulates IgA selection and bacterial composition in the gut.

Immunoglobulin A (IgA) is essential to maintain the symbiotic balance between gut bacterial communities and the host immune system. Here we provide evidence that the inhibitory co-receptor programmed cell death-1 (PD-1) regulates the gut microbiota through appropriate selection of IgA plasma cell repertoires. PD-1 deficiency generates an excess number of T follicular helper (T(FH)) cells with altered phenotypes, which results in dysregulated selection of IgA precursor cells in the germinal center of Peyer's patches. Consequently, the IgAs produced in PD-1-deficient mice have reduced bacteria-binding capacity, which causes alterations of microbial communities in the gut. Thus, PD-1 plays a critical role in regulation of antibody diversification required for the maintenance of intact mucosal barrier.

A shuttling molecular machine with reversible brake function.

Design, synthesis, and demonstration of a prototype of a shuttling molecular machine with a reversible brake function are reported. It is a photochemically and thermally reactive rotaxane composed of a dianthrylethane-based macrocycle as the ring component and a dumbbell shaped molecular unit with two, secondary ammonium stations separated by a phenylene spacer as the axle component. The rate of shuttling motion was shown to be reduced to less than 1 % (from 340 to <2.5 s(-1)) by reducing the size of the ring component from 30-crown-8 to 24-crown-8 macrocycles upon photoirradiation. The ring component was turned back to 30-crown-8 by thermal ring opening, thus establishing a reversible brake function that works in response to photochemical and thermal stimuli.

Highly effective and reversible control of the rocking rates of rotaxanes by changes to the size of stimulus-responsive ring components.

We have designed and synthesized rotaxanes whose rates of rocking motion (pendular motion) were switched reversibly through changes to the size of the ring component in response to external stimuli. The ring molecules of the rotaxanes incorporate a metaphenylene unit, which swings like a pendulum, and a dianthrylethane unit, which undergoes reversible isomerization in response to photo- and thermal stimuli and changes the size of the ring component. The rocking rates were estimated quantitatively by variable-temperature (VT) NMR spectroscopy and saturation transfer experiments, which revealed substantial changes in the rates between the open and closed forms, particularly in the case of rotaxanes with an isopropoxy group attached to a phenylene unit.

An anthracene-based photochromic macrocycle as a key ring component to switch a frequency of threading motion.

A concept and demonstration of a switching in frequencies of molecular motions are described using a pseudorotaxane system. The setup consists of dibenzylammonium hexafluorophosphate and a photochromic dianthrylethane-based [24]crown-8-type macrocycle, which we designed as a key ring component for the pseudorotaxane system having photocontrollable threading functionality by changing the size of ring component due to the action of light.

Two distinctive pathways for recruitment of naive and primed IgM+ B cells to the gut lamina propria.

Intestinal IgA+ B cells are generated from IgM+ B cells by in situ class switching in two separate gut microenvironments: organized follicular structures and lamina propria (LP). However, the origin of IgM+ B cells in the gut LP is unknown. Transfer experiments to reconstitute IgM+ B cells and IgA plasma cells in LP of aly/aly mice, which are defective in all organized follicular structures because of an NF-kappaB-inducing kinase (NIK) mutation, revealed that naive B cells can directly migrate to the LP. This migration requires NIK-dependent activation of gut stromal cells. By contrast, the entry of gut-primed IgM+ B cells to the LP is independent of stromal cells with functional NIK. Our results indicate that naive B cells directly migrate to the LP by a distinct pathway from gut-primed B cells.

Aberrant expansion of segmented filamentous bacteria in IgA-deficient gut.

The mechanism to maintain homeostasis of the gut microbiota remains largely unknown despite its critical role in the body defense. In the intestines of mice with deficiency of activation-induced cytidine deaminase (AID), the absence of hypermutated IgA is partially compensated for by the presence of large amounts of unmutated IgM and normal expression levels of defensins and angiogenins. We show here a predominant and persistent expansion of segmented filamentous bacteria throughout the small intestine of AID(-/-) mice. Reconstitution of lamina propria IgA production in AID(-/-) mice recovered the normal composition of gut flora and abolished the local and systemic activation of the immune system. The results indicate that secretions of IgAs rather than innate defense peptides are critical to regulation of commensal bacterial flora and that the segmented filamentous bacteria antigens are strong stimuli of the mucosal immune system.