Medial vascular calcification is common in chronic kidney disease patients and linked to hyperphosphatemia. Upon phosphate exposure, intricate signaling events orchestrate pro-calcific effects in the vasculature mediated by vascular smooth muscle cells (VSMCs). Sphingosine kinase 1 (SPHK1) produces sphingosine-1-phosphate (S1P) and is associated with complex effects in the vascular system. The present study investigated a possible involvement of SPHK1 in VSMC calcification. Experiments were performed in primary human aortic VSMCs under pro-calcific conditions, with pharmacological inhibition or knockdown of SPHK1 or SPNS2 (a lysolipid transporter involved in cellular S1P export), as well as in Sphk1-deficient and wild-type mice treated with cholecalciferol. In VSMCs, SPHK1 expression was up-regulated by pro-calcific conditions. Calcification medium up-regulated osteogenic marker mRNA expression and activity as well as calcification of VSMCs, effects significantly augmented by co-treatment with the SPHK1 inhibitor SK1-IN-1. SK1-IN-1 alone was sufficient to up-regulate osteogenic signaling in VSMCs during control conditions. Similarly, the SPHK1 inhibitor PF-543 and SPHK1 knockdown up-regulated osteogenic signaling in VSMCs and aggravated VSMC calcification. In contrast, co-treatment with the SPNS2 inhibitor SLF1081851 suppressed osteogenic signaling and calcification of VSMCs, effects abolished by silencing of SPHK1. In addition, Sphk1 deficiency aggravated vascular calcification and aortic osteogenic marker expression in mice after cholecalciferol overload. In conclusion, SPHK1 inhibition, knockdown, or deficiency aggravates vascular pro-calcific signaling and calcification. The reduced calcification after inhibition of S1P export suggests a possible involvement of intracellular S1P, but further studies are required to elucidate the complex roles of SPHKs and S1P signaling in calcifying VSMCs.

Background: A decrease in governmental vaccination initiatives and diminishing public enthusiasm for vaccines could jeopardize vaccine uptake, potentially endangering those who are most at risk. In this survey study, we evaluated the current acceptance rates of the newly developed monovalent XBB1.5-adapted COVID-19 vaccine among kidney transplant recipients and dialysis patients in Austria and Israel and identified factors influencing vaccine acceptance. Methods: The survey involved a total of 656 patients aged 18 and older and was carried out from 20 November to 21 December 2023, at the Medical University of Vienna, Austria and the Rabin Medical Center in Petah Tikva, Israel. Logistic regression analysis was used to explore the relationships between vaccine acceptance and variables such as age, gender, country, past COVID-19 infection status and severity, renal replacement therapy, education level, and willingness to receive the annual flu vaccine. Results: The survey showed that 54% of patients in Austria and 63% in Israel expressed acceptance of the modified XBB1.5-adapted COVID-19 vaccine. The main hesitancy was due to concerns about potential side effects, with 44% in Austria and 53% in Israel expressing apprehension. A willingness to receive the influenza vaccine, older age in Austria, and kidney transplant status in Israel were key predictors of greater COVID-19 vaccine acceptance. Conclusions: This study showed that more than 50% of our kidney transplant recipients and dialysis patients were willing to receive the adapted COVID-19 vaccine. Yet, vaccine hesitancy remained a significant barrier even among these high-risk groups, despite the availability of an updated COVID-19 vaccine targeting the Omicron subvariant XBB1.5.

Anti-SARS-CoV-2 vaccination of dialysis patients has been proven to be safe and effective to reduce COVID-19-related morbidity and mortality. However, data on the durability of anti-SARS-CoV-2 antibodies post-vaccination in peritoneal dialysis (PD) patients are scarce. In this prospective single-center cohort study we measured anti-SARS-CoV-2 RBD antibodies 3 and 6 months after the 3rd dose of the mRNA-1273 vaccine in 27 adult PD patients and recorded breakthrough infections. Furthermore, in a mixed model analysis, we analyzed potential factors influencing the humoral response following vaccination. Anti-SARS-CoV-2 RBD antibody levels declined from 21,424 BAU/mL at 1 month to 8397 BAU/mL at 3 months and to 5120 BAU/mL at 6 months after the 3rd dose, but remained higher than pre-3rd dose levels (212 BAU/mL). Eight patients (29.6%) were infected with SARS-CoV-2 within six months from the 3rd dose during the Omicron wave. Previous high antibody levels, high glomerular filtration rate (GFR) and low Davies Comorbidity Score were associated with higher anti-SARS-CoV-2 antibody levels after the booster. In conclusion, PD patients exhibited a robust and durable humoral response after a third dose of the mRNA-1273 vaccine. A high GFR and low comorbidity as well as previous high antibody levels predicted a better humoral response to vaccination.

In dialysis patients the humoral response to anti-SARS-CoV-2 vaccines is attenuated and rapidly declines over time. However, data on the persistence of the immune response in peritoneal dialysis (PD) patients are scarce, particularly after a third (booster) dose with mRNA-1273 vaccine. In this prospective cohort study, we report anti-SARS-CoV-2 antibody levels in PD patients before and after the third dose of mRNA-1273 vaccine. Six months after the second dose, anti-SARS-CoV-2 antibodies were detected in all patients (n = 34). However, within this time period antibodies substantially declined in 31 of 34 patients (4.5-fold, median = 192 BAU/mL, p = 1.27 × 10–9) and increased in three patients. In accordance with government regulations, a third dose of mRNA-1273 vaccine (50 μg) was given to 27 PD patients 6 months after the second dose which induced a significant increase of anti-SARS-CoV-2 antibody titers (58.6-fold, median = 19405 BAU/mL, p = 1.24 × 10–29). A mixed model analysis showed that a lower Davies Comorbidity Score and a higher GFR were associated with higher antibody titers (p = 0.03 and p = 0.02). The most common adverse events after the third dose were pain at the injection site (77.8%) and fatigue (51.9%). No hospitalizations were reported. In conclusion, 6 months after the second dose of mRNA-1273 vaccine, anti-SARS-CoV-2 antibodies substantially decreased in PD patients, whereas a well-tolerated third dose induced a robust humoral response. Our data suggest that the administration of a booster dose within a shorter interval than 6 months should be considered in PD patients in order to maintain high anti-SARS-CoV-2 antibody levels and assure protection from severe COVID-19 disease.

BackgroundDialysis patients are at high risk for a severe clinical course after infection with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Safety and early immune responses after mRNA-based vaccination have been reported mostly in patients on hemodialysis (HD), whereas reports of peritoneal dialysis (PD) patients remain rare.MethodsIn this retrospective observational study, 39 PD patients had received two doses of the mRNA-1273 Moderna® vaccine. We analyzed SARS-CoV-2 Spike (S) antibody titers 4 weeks after each dose of mRNA-1273 and report local and systemic side effects in PD patients that occurred within one week after each mRNA-1273 dose. Using a quantile regression model we examined factors that might influence SARS-CoV-2 S antibody levels in PD patients.ResultsFour weeks after the first dose of mRNA-1273 vaccine 33 of 39 (84.6%) PD patients seroconverted and presented with 6.62 U/mL (median; IQR 1.57-22.5) anti-SARS-CoV-2 S antibody titers. After the second dose, 38 of 39 (97.4%) PD patients developed anti-SARS-CoV-2 S antibodies and titers increased significantly (median 968 U/mL; IQR 422.5-2500). Pain at the injection site was the most common local adverse event (AE) (71%). Systemic AEs occurring after the first dose were mostly fatigue (33%) and headache (20%). No severe systemic AEs were reported after the first injection. After the second dose the incidence and the severity of the systemic AEs increased. The most common systemic AEs were: fatigue (40.5%), headache (22.5%), joint pain (20%), myalgia (17.5%) and fever (13%). Lower Davies Comorbidity Score (p=0.04) and shorter dialysis vintage (p=0.017) were associated with higher antibody titers after the first dose. Patients with higher antibody titers after the first dose tended to have higher antibody titers after the second dose (p=1.53x10-05).ConclusionsPeritoneal dialysis patients in this cohort had a high seroconversion rate of 97.4%, showed high antibody titers after full vaccination and tolerated the anti-SARS-CoV-2 mRNA-1273 vaccine well without serious adverse events.

BACKGROUND Acid base and electrolyte disorders are frequently reported in the early period after renal transplantation. No comprehensive data exist on the prevalence and patterns of, and contributing factors to, electrolyte disturbances in patients with stable long-term allograft function. METHODS We analysed 576 renal transplant recipients (serum creatinine level <2.0 mg/dl) in a cross-sectional study to evaluate the prevalence of electrolyte disorders and the risk factors associated with their occurrence. RESULTS A total of 369 patients (64%) of all allograft recipients (n = 576) showed at least one electrolyte and acid base disorder. The most abundant disorder was hypomagnesaemia (25%, n = 143), followed by hyperkalaemia (12.8%, n = 74), hypercalcaemia (12%, n = 69), hypophosphataemia (11.6%, n = 67), metabolic acidosis (11.1%, n = 61) and hyponatraemia (9%, n = 52). All other electrolyte disorders were rare (<6%). In most cases the electrolyte disorders could be classified as mild. Forty percent of the cases had a combined disorder, but without a preferential pattern of combinations. In a multivariate logistic regression analysis, the most important factors contributing significantly to the occurrence of electrolyte disorders were renal function and concomitant medications. CONCLUSION Acid base and electrolyte disorders are frequently observed in stable renal allograft recipients, but are usually mild. A combination of two or more electrolyte abnormalities often occurs, although no predominant pattern of a unique combination of electrolyte disorder is recognizable.

Background Complement factor C3 represents the central component of the complement cascade and its activation split product C3a plays an important role in inflammation and disease. Many human disorders are linked to dysregulation of the complement system and alteration in interaction molecules. Therefore, various therapeutic approaches to act on the complement system have been initiated. Methods and Results Aiming to develop a tool to eliminate C3a/C3 from the circulation, in a first step a high affine murine monoclonal antibody (mAb) (3F7E2-mAb) was generated against complement factor C3 and selected for binding to the C3a region to serve as immunoaffinity reagent. Functional testing of the 3F7E2-mAb revealed an inhibition of Zymosan-induced cleavage of C3a from C3. Subsequently, a C3a/C3 specific 3F7E2-immunoaffinity column was developed and apheresis of C3a/C3 and associates was performed. Finally, a proteomic analysis was carried out for identification of apheresis products. C3a/C3 was liberated from the 3F7E2-column together with 278 proteins. C3a/C3 interaction specificity was validated by using a haptoglobin immunoaffinity column as control and biostatistic analysis revealed 39 true C3a/C3 interactants. Conclusion A novel and functionally active mAb was developed against complement factor C3a/C3 and used in a specific immunoaffinity column that allows apheresis of C3a/C3 and associates and their identification by proteomic analysis. This methodological approach of developing specific antibodies that can be used as immunoaffinity reagents to design immunoaffinity columns for elimination and further identification of associated proteins could open new avenues for the development of tailored immunotherapy in various complement-mediated or autoimmune diseases.

Senescent cells accumulate during ageing in various tissues and contribute to organismal ageing. However, factors that are involved in the induction of senescence in vivo are still not well understood. SNEV(P) (rp19/) (PSO) (4) is a multifaceted protein, known to be involved in DNA damage repair and senescence, albeit only in vitro. In this study, we used heterozygous SNEV(+/-) mice (SNEV-knockout results in early embryonic lethality) and wild-type littermate controls as a model to elucidate the role of SNEV(P) (rp19/) (PSO) (4) in DNA damage repair and senescence in vivo. We performed PUVA treatment as model system for potently inducing cellular senescence, consisting of 8-methoxypsoralen in combination with UVA on mouse skin to induce DNA damage and premature skin ageing. We show that SNEV(P) (rp19/) (PSO) (4) expression decreases during organismal ageing, while p16, a marker of ageing in vivo, increases. In response to PUVA treatment, we observed in the skin of both SNEV(P) (rp19/) (PSO) (4) and wild-type mice an increase in γ-H2AX levels, a DNA damage marker. In old SNEV(P) (rp19/) (PSO) (4) mice, this increase is accompanied by reduced epidermis thickening and increase in p16 and collagenase levels. Thus, the DNA damage response occurring in the mouse skin upon PUVA treatment is dependent on SNEV(P) (rp19/) (PSO) (4) expression and lower levels of SNEV(P) (rp19/) (PSO) (4) , as in old SNEV(+/-) mice, result in increase in cellular senescence and acceleration of premature skin ageing.

www.jidonline.org S61 349 Oxidative stress and mitochondrial alterations in Kindler Syndrome S Guerrero-Aspizua, Z Elisabeth, JL García-Giménez, M García, CJ Conti, F Larcher, FV Pallardó and M del Río 1 Physiology, Fundación Investigación Hospital Clínico Universitario de Valencia, Instituto de Investigación INCLIVA, Valencia, Spain and 2 Bioengineering, Unidad Mixta UC3M-CIEMAT. CIBERER, Madrid, Spain Kindler Syndrome (KS) (OMIM 173650) is an autosomal recessive skin disorder caused by mutations in FERMT 1 and characterized by skin blistering, photosensitivity, premature aging and skin cancer predisposition. However, the known functions of FERMT1, involved in cell adhesion, do not suffice to fully understand the pleiotropic nature and clinical variability of this genodermatosis. Some of these pathognomonic features of KS not related to cutaneous fragility, such as premature skin aging and cancer predisposition, have been strongly associated with oxidative stress. Mitochondrial oxidative stress has long been implicated in both, aging and cancer. During oxidative phosphorylation, reactive oxygen species (ROS) are generated as by-products and its accumulation results in DNA damage as well as increased cancer susceptibility. We have explored the potential role of mitochondria-derived oxidative stress on the pathogenesis of KS. For that purpose we studied different biomarkers of oxidative stress in cells from KS patients. Patient-derived keratinocytes showed an altered oxidative status as demonstrated by increased glutathione and malondialdehyde levels and by a highly sensitive chimerical redox biosensor system. The ultrastructural analysis of KS skin biopsies and keratinocytes revealed striking abnormalities in mitochondria. In addition, keratinocytes from KS patients showed a reduced and diffuse MitoTracker Red staining and a significant reduction of the membrane potential. Overall, our data indicate that mitochondria in KS are not only altered in structure, but also in their distribution and functionality. This is the first study to demonstrate that mitochondrial dysfunction and oxidative stress contribute to the etiology of KS. 350 Regulation of IL-33 expression by normal human epidermal keratinocyte H Tsuda, M Komine, T Ohshio, S Tominaga and M Ohtsuki 1 Dermatology, Jichi Medical University, Shimotuke, Japan and 2 Biochemistry, Jichi Medical University, Shimotuke, Japan IL-33 is a member of the IL-1 family, and important to adaptive Th2 immunity. We previously reported that IFNγ induced expression of IL-33 in normal human epidermal keratinocytes (NHEKs). On the other hand, it has been reported that IFNγ did not induce IL-33 in monocyte, while TNFα and IL-1β did. Recently mouse IL-33 (mIL33) has been revealed to have two distinct transcripts with different non-coding exon1, both of which code the same protein sequences. We have confirmed that there were three different transcription products of IL-33, each containing one of three distinct exon1s, i.e., exon1a, 1b and 1c. We speculated that each exon1 has its own promoter region, which may be regulated in cell typeand stimulus-dependent manner. We aimed to clarify the differential usage of three distinct promoters containing each exon1 in different types of cells, with various stimuli. We amplified approximately 2.5 kbp region of the 5’ UTR of each three exon1 with PCR and cloned them into upstream of firefly luciferase gene construct. These constructs were transfected to NHEKs, human umbilical endothelial cells (HUVECs) and normal human dermal fibroblasts (NHDFs), stimulated with IFNγ or TNFα, and luciferase assay was performed. The construct containing 5’ UTR of exon1b had high luciferase activity without stimulation in NHEKs, HUVECs, and NHDFs. It strongly responded to IFNγ, but did not respond to other stimuli investigated, such as TNFα, IL-1β and LPS for TLR4 ligand in NHEKs and HUVECs. In NHDFs, exon1b containing promoter construct did not respond to any stimuli investigated. Other constructs containing 5’ UTR of exon1a or exon1c, showed only very weak luciferase activity, which did not respond to any stimuli investigated. We identified an active promoter of hIL33. The regulation of IL-33 transcription in NHEKs, HUVECs, and NHFDs may depend on the same promoter, which may utilize common transcription factors.

Current vaccine conditions predominantly elicit low-avidity cytotoxic T lymphocytes (CTLs), which are non-tumor-cytolytic but indistinguishable by tetramer staining or enzyme-linked immunospot from high-avidity CTLs. Using CTL clones of high or low avidity for melanoma antigens, we show that low-avidity CTLs can inhibit tumor lysis by high-avidity CTLs in an antigen-specific manner. This phenomenon operates in vivo: high-avidity CTLs control tumor growth in animals but not in combination with low-avidity CTLs specific for the same antigen. The mechanism involves stripping of specific peptide-major histocompatibility complexes (pMHCs) via trogocytosis by low-avidity melanoma-specific CTLs without degranulation, leading to insufficient levels of specific pMHC on target cell surface to trigger lysis by high-avidity CTLs. As such, peptide repertoire on the cell surface is dynamic and continually shaped by interactions with T cells. These results describe immune regulation by low-avidity T cells and have implications for vaccine design.

BACKGROUND:Acute graft-versus-host disease (aGVHD) poses a major limitation for broader therapeutic application of allogeneic hematopoietic cell transplantation (allo-HCT). Early diagnosis of aGVHD remains difficult and is based on clinical symptoms and histopathological evaluation of tissue biopsies. Thus, current aGVHD diagnosis is limited to patients with established disease manifestation. Therefore, for improved disease prevention it is important to develop predictive assays to identify patients at risk of developing aGVHD. Here we address whether insights into the timing of the aGVHD initiation and effector phases could allow for the detection of migrating alloreactive T cells before clinical aGVHD onset to permit for efficient therapeutic intervention.METHODS:Murine major histocompatibility complex (MHC) mismatched and minor histocompatibility antigen (miHAg) mismatched allo-HCT models were employed to assess the spatiotemporal distribution of donor T cells with flow cytometry and in vivo bioluminescence imaging (BLI). Daily flow cytometry analysis of peripheral blood mononuclear cells allowed us to identify migrating alloreactive T cells based on homing receptor expression profiles.RESULTS:We identified a time period of 2 weeks of massive alloreactive donor T cell migration in the blood after miHAg mismatch allo-HCT before clinical aGVHD symptoms appeared. Alloreactive T cells upregulated α4β7 integrin and P-selectin ligand during this migration phase. Consequently, targeted preemptive treatment with rapamycin, starting at the earliest detection time of alloreactive donor T cells in the peripheral blood, prevented lethal aGVHD.CONCLUSIONS:Based on this data we propose a critical time frame prior to the onset of aGVHD symptoms to identify alloreactive T cells in the peripheral blood for timely and effective therapeutic intervention.

In BDC2.5NOD mice, a spontaneous model of Type 1 diabetes, CD4+T cells express a transgene-encoded T-cell receptor with reactivity against a pancreatic antigen. This leads to a massive infiltration and destruction of the pancreatic islets and subsequent diabetes. When we reconstituted lethally irradiated lymphocyte-deficient B6.g7 (I-Ag7+) Rag-/- mice with BDC2.5NOD (ckit+Lin-Sca-1hi) hematopoietic stem and progenitor cells (HSPC), the recipients exhibited hyperglycemia and succumbed to diabetes. Surprisingly, lymphocyte-sufficient B6.g7 mice reconstituted with BDC2.5NOD HSPCs were protected from diabetes. In this study we investigated the factors responsible for attenuation of diabetes in the B6.g7 recipients. Analysis of chimerism in the B6.g7 recipients showed that although B cells and myeloid cells were 98% donor-derived, the CD4+ T cell compartment contained ~50% host-derived cells. These host-derived CD4+ T cells were enriched for conventional Tregs (CD25+Foxp3+) and also for host-derived CD25-Foxp3- CD4+ T cells that express markers of suppressive function, CD73, FR4 and CD39. Though negative selection did not eliminate donor-derived CD4+ T cells in the B6.g7 recipients, these cells were functionally suppressed. Thus host-derived CD4+ T cells that emerge in mice following myeloablation exhibit a regulatory phenoytpe and likely attenuate autoimmune diabetes. These cells may provide new therapeutic strategies to suppress autoimmunity.

Carina A Bäuerlein (Baeuerlein_C@medizin.uni-wuerzburg.de) Simone S Riedel (Riedel_S1@medizin.uni-wuerzburg.de) Jeanette Baker (jmbe@stanford.edu) Christian Brede (brede_c@medizin.uni-wuerzburg.de) Ana-Laura Jordán Garrote (E_Jordan_A@medizin.uni-wuerzburg.de) Martin Chopra (chopra_m@medizin.uni-wuerzburg.de) Miriam Ritz (ritz_m1@medizin.uni-wuerzburg.de) Georg F Beilhack (gbeilhack@gmail.com) Stephan Schulz (stephan.schulz@charite.de) Robert Zeiser (robert.zeiser@uniklinik-freiburg.de) Paul G Schlegel (schlegel_p@kinderklinik.uni-wuerzburg.de) Hermann Einsele (einsele_h@medizin.uni-wuerzburg.de) Robert S Negrin (negrs@stanford.edu) Andreas Beilhack (beilhack_a@medizin.uni-wuerzburg.de)

OBJECTIVE:In the K/BxN mouse model of inflammatory arthritis, T cells carrying a transgenic T cell receptor initiate disease by helping B cells to produce arthritogenic anti-glucose-6-phosphate isomerase (anti-GPI) autoantibodies. We found that lethally- irradiated lymphocyte-deficient C57BL/6 (B6).g7 (I-A(g7) +) recombinase-activating gene-deficient (Rag(-/-)) mice reconstituted with K/BxN hematopoietic stem and progenitor cells exhibit arthritis by week 4. In contrast, healthy B6.g7 recipients of K/BxN hematopoietic stem and progenitor cells show only mild arthritis, with limited extent and duration. The objective of this study was to investigate the factors responsible for the attenuation of arthritis in B6.g7 recipients.METHODS:Antibody responses were measured by enzyme-linked immunosorbent assay. Fluorescence-activated cell sorting analyses were performed for testing chimerism, expression of markers of activation and suppression, tetramer binding, and intracellular cytokines in CD4+ T cells. Suppressive activity of CD4+ T cells was studied by adoptive transfer.RESULTS:Titers of anti-GPI antibodies in reconstituted B6.g7 mice were ∼60-fold lower than in reconstituted B6.g7 Rag(-/-) mice. Examination of chimerism in the reconstituted B6.g7 mice showed that B cells and myeloid cells in these mice were donor derived, but CD4+ T cells were primarily host derived and enriched for cells expressing the conventional regulatory markers CD25 and FoxP3. Notably, CD4+CD25-FoxP3- T cells expressed markers of suppressive function (CD73 and folate receptor 4), and delayed disease after adoptive transfer. Activation of donor-derived CD4+ T cells was reduced, and thymic deletion of these cells appeared increased.CONCLUSION:Despite myeloablation, host CD4+ T cells having a regulatory phenotype emerge in these mice and attenuate autoimmunity.

OBJECTIVES:In chronic kidney disease-mineral and bone disorder (CKD-MBD), most treatment decisions are guided by parathyroid hormone (PTH) levels. Here, we aimed at assessing the technical and clinical performance of two novel automated biointact PTH(1-84) assays, from Roche Diagnostics (Ro) and DiaSorin (DS), in hemodialysis patients. DESIGN AND METHODS:We recorded demographics, dialysis treatment characteristics, pharmacotherapy for CKD-MBD and laboratory work-up. Statistical methods included Passing-Bablok, and multiple linear regression. RESULTS:121 patients, dialyzing on average for 3.5 years (range: 0.1-22.5), with serum phosphate 1.9±0.6 mmol/L (mean±SD), participated in the study. Median serum concentration for intact PTH was 223 ng/L (range: 5-2844), and for biointact PTH(1-84) was 136 ng/L (Ro; range: 1-1644), respectively 138 ng/L (DS; range: 4-1580). Both biointact assays were significantly correlated (r=0.98; Ro=0.87×DS+19.60). Bland-Altmann plots revealed an average bias ±2 SD of 10±27 ng/L below 200 ng/L, and -32±157 ng/L above 200 ng/L (Ro minus DS). The variably adjusted association between PTH and serum phosphate was very similar, regardless of the PTH assay, but this was not the case for PTH-derived measures (ratios biointact/intact; differences intact minus biointact). (Log)PTH concentrations as well as serum phosphate were significantly associated with serum creatinine, but only in patients with >0 mL urine per day. CONCLUSIONS:Results from Roche and DiaSorin biointact PTH(1-84) assays were well correlated, but showed increased deviations at higher concentrations. Biointact PTH(1-84) levels are roughly two third of intact PTH. The association between PTH and serum creatinine may depend on residual renal clearance of PTH and/or serum phosphate.

Abstract In the K/BxN mouse model of inflammatory arthritis, T cells carrying a transgenic TCR initiate disease by helping B cells to produce arthritogenic anti-GPI (glucose-6- phosphate isomerase) autoantibodies. We found that lethally-irradiated lymphocyte-deficient B6.g7 (I-Ag7+) Rag-/- mice reconstituted with K/BxN HSC (ckit+Lin-Sca-1hi) exhibit arthritis by week 4 and have anti-GPI Ab levels comparable to K/BxN mice. The normal B6.g7 mouse recipients of KBN HSC, however, showed only a mild arthritis with limited extent and duration. Titers of anti-GPI Abs in reconstituted B6.g7 mice were ~60 fold lower than in K/BxN mice. To investigate the basis of this attenuated autoimmunity, we examined the chimerism in the reconstituted B6.g7 mice. Although the B cell and myeloid compartments in blood and spleen had 98%±0.1 donor-derived cells, the CD4+ T cells were only 12%± 2.5 donor-derived. Further, host-derived CD4+ T cells in the reconstituted B6.g7 mice were 18%±3.5 CD25+FoxP3+ Treg cells compared to 8%±1.76 Tregs in donor-derived CD4+ T cells (P<0.024). Notably, attenuation of autoimmune diabetes and high percentage of host-derived Tregs (hTreg) were also observed when B6.g7 mice were reconstituted with HSCs from BDC2.5 transgenic mice. The hTreg were functional in vitro in standard assays. Our findings show that despite myeloablation, hTreg emerge in these mice and attenuate autoimmunity.