A Case of Mesangial Proliferative Nephritis Caused by Slow Cryoglobulin.

The patient was a woman in her 60s. She was found to have proteinuria on a health checkup. She did not have any particular subjective symptoms, and no definitive diagnosis was made, despite serological findings indicative of immune abnormalities. A renal biopsy was performed. Light microscopy of renal tissue section revealed mesangial proliferative nephritis. Electron microscopic findings included electron-dense deposits and fibrillar/tubular structures with a diameter of 20-30 nm. These findings suggested the presence of cryoglobulin (CG), but CG was not detected in qualitative or quantitative hematologic tests. Thus, the serum samples were stored at 37°C for a long period of time and then cooled to 4°C. When the obtained precipitates were examined, CG was successfully detected. CG that precipitates only after a long period of time is referred to as slow cryoglobulin (sCG), and sCG is extremely rare. The present case is the first documented case, to our knowledge, of renal disorders caused by sCG. It should be noted that there are some cases in which it takes much time for CG to precipitate. Thus, when CG cannot be detected, it is necessary to spend much time to determine whether CG precipitates.

The risk of weekend biopsy: Impact of specimen source and fixation status on HER2 assessment in the treatment of advanced gastric cancer (The HER_WEEKEND study).

Accurate evaluation of human epidermal growth factor receptor type 2 (HER2) expression is crucial for determining chemotherapy regimens in gastric cancer. However, formalin fixation status has been identified as an important factor affecting HER2 assessment reliability. This retrospective cohort study aimed to investigate the correlation between sample collection day (weekday vs. weekend) and source (biopsy vs. surgical specimens) in assessing HER2 expression in patients with unresectable advanced/recurrent gastric cancer. Data were collected from gastric cancer patients who received chemotherapy at a single public hospital in Japan from 2008 to 2021. The analysis included 177 patients (109 men, 68 women) with a median age of 68.0 (21-88) years, and the primary outcome was the HER2 positivity rate. The overall HER2 positivity rate was 18.1%, with higher rates on weekdays (20.0%) compared to weekends (12.8%). Biopsies had higher positivity rates on weekdays (23.9%) but lower rates on weekends (11.1%) than surgical specimens. Significant differences were observed in formalin fixation times between weekdays and weekends for both biopsies and surgical samples. The study findings suggest that longer formalin fixation times on weekends may lead to underestimating HER2 expression, particularly in biopsies. Therefore, it is crucial to be cautious of excessive formalin fixation when collecting samples, especially during weekend biopsies.

BK Polyomavirus-Associated Urothelial Carcinoma of the Bladder with a Background of BK Polyomavirus Nephropathy in a Kidney Transplant Recipient.

Renal transplant recipients are at increased risk for the development of a malignant neoplasm. Polyomavirus-associated urothelial carcinoma is a rare tumor that occurs in renal transplant recipients, with approximately 41 cases reported since 2002. It accounts for 27-31% of all post-transplant urothelial carcinomas and develops at an average of 8.5 years after transplantation. Histologically, it shows high-grade urothelial carcinoma (95.1%) with a high frequency of glandular differentiation and micropapillary structures (58.5%) and positive immunohistochemistry for polyomavirus large T antigen, p53 (92.9%), and p16 (100%). We encountered a case of BK polyomavirus (BKPyV)-associated urothelial carcinoma of the bladder diagnosed 54 months after kidney transplantation. Histologically, it was a high-grade urothelial carcinoma with micropapillary features, and immunohistochemically, it was diffusely positive for polyomavirus large T antigen, p16, and p53. BKPyV DNA and mRNA for BKPyV large T antigen have been identified in tissues using real-time polymerase chain reaction. The same sequence of the BKPyV VP1 genome hypervariable region was detected in both transplanted kidney tissue with polyomavirus nephropathy and urothelial carcinoma tissue, suggesting that polyomavirus-associated urothelial carcinoma developed in a background of persistent polyomavirus nephropathy. This case showed typical histological features and was detected and treated at an earlier stage than has been reported. It is important to keep in mind that polyomavirus-associated urothelial carcinoma can develop early after transplantation and might be associated with polyomavirus nephropathy. Because of its rapidly progressive nature, careful follow-up with urine cytology and cystoscopy is necessary. We report this case with a literature review.

Regulation of NETosis and Inflammation by Cyclophilin D in Myeloperoxidase-Positive Antineutrophil Cytoplasmic Antibody-Associated Vasculitis.

OBJECTIVE: Antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) is pathologically characterized by focal fibrinoid necrosis, in which ANCA-mediated neutrophil extracellular trap (NET) formation and subsequent endothelial cell necrosis occur. Cyclophilin D (CypD) plays an important role in mediation of cell necrosis and inflammation via the opening of mitochondrial permeability transition pores. This study was undertaken to examine the role of CypD in AAV pathogenesis. METHODS: We assessed the role and mechanism of CypD in ANCA-stimulated neutrophils in vitro by immunostaining and electron microscopy observation. We performed a comprehensive RNA-sequencing analysis on ANCA-treated murine neutrophils. To investigate the role of CypD in vivo, we assessed disease features in CypD-knockout mice and wild-type mice using 2 different murine AAV models: anti-myeloperoxidase IgG transfer-induced AAV and spontaneous AAV. RESULTS: In vitro experiments showed that pharmacologic and genetic inhibition of CypD suppressed ANCA-induced NET formation via the suppression of reactive oxygen species and cytochrome c release from the mitochondria. RNA-sequencing analyses in ANCA-treated murine neutrophils revealed the involvement of inflammatory responses, with CypD deficiency reducing ANCA-induced alterations in gene expression. Furthermore, analyses of upstream regulators revealed the relevance of intracellular calcium (CypD activator) and cyclosporin (CypD inhibitor) in ANCA stimulation, indicating that the CypD-dependent opening of mitochondrial permeability transition pores is associated with ANCA-induced neutrophil activation and NETosis. In both AAV mouse models, the genetic deletion of CypD ameliorated crescentic glomerulonephritis via the inhibition of CypD-dependent neutrophil and endothelial necrosis. CONCLUSION: CypD targeting is a novel and specific therapeutic strategy for AAV via the resolution of necrotizing vasculitis.

Soluble Interleukin-2 Receptor Predicts Treatment Outcome in Patients With Autoimmune Tubulointerstitial Nephritis. A Preliminary Study.

Background: Autoimmune tubulointerstitial nephritis (TIN) is characterized by immune-mediated tubular injury and requires immunosuppressive therapy. However, diagnosing TIN and assessing therapeutic response are challenging for clinicians due to the lack of useful biomarkers. Pathologically, CD4+ T cells infiltrate to renal tubulointerstitium, and soluble interleukin-2 receptor (sIL-2R) has been widely known as a serological marker of activated T cell. Here, we explored the usefulness of serum sIL-2R to predict the treatment outcome in patients with autoimmune TIN. Methods: Study Design: Single-center retrospective observational study. Participants: 62 patients were diagnosed of TIN from 2005 to April 2018 at Hokkaido University Hospital. Among them, 30 patients were diagnosed with autoimmune TIN and treated with corticosteroids. We analyzed the association between baseline characteristics including sIL-2R and the change of estimated glomerular filtration rate (eGFR) after initiation of corticosteroids. Results: The serum sIL-2R level in patients with autoimmune TIN was significantly higher than that in chronic kidney disease patients with other causes. Mean eGFR in autoimmune TIN patients treated with corticosteroids increased from 43.3 ± 20.4 mL/min/1.73 m2 (baseline) to 50.7 ± 19.9 mL/min/1.73 m2 (3 months) (ΔeGFR; 22.8 ± 26.0%). Multivariate analysis revealed that higher sIL-2R (per 100 U/mL, ß = 1.102, P < 0.001) level was independently associated with the renal recovery. In ROC analysis, sIL-2R had the best area under the curve value (0.805) and the cutoff point was 1182 U/mL (sensitivity = 0.90, 1-specificity = 0.45). Conclusions: Our study showed that elevated serum sIL-2R levels might become a potential predictive marker for therapeutic response in autoimmune TIN.

Comparison of administration of single- and triple-course steroid pulse therapy combined with tonsillectomy for immunoglobulin A nephropathy.

ABSTRACT: Immunoglobulin A nephropathy (IgAN) is a form of chronic glomerulonephritis that can cause end-stage renal disease. Recently, tonsillectomy combined with corticosteroid pulse (TSP) has been shown to be effective for achieving clinical remission and favorable renal outcome in patients with IgAN. However, the standard regimen of corticosteroid use in TSP has not been established. Herein, we compared the effect of single- or triple-course steroid pulse therapy combined with tonsillectomy in patients with IgAN.This retrospective, observational cohort study included 122 patients with IgAN enrolled from January 2004 to December 2018 at 2 independent institutions. We divided the patients into 2 groups; single-course (TSP1: n = 70) and triple-course (TSP3: n = 52) of corticosteroid pulse therapy (1 course comprised 3 consecutive days' infusion of 0.5 g methylprednisolone) combined with tonsillectomy. The primary outcome for renal survival was defined as the first occurrence of ≧30% decrease in estimated glomerular filtration rate from baseline. Secondary outcomes included the incidence of clinical remission and recurrence of the disease.Regarding clinical parameters and findings at baseline, there were no significant differences between the 2 groups. The 8-years renal survival in the 2 groups was not significantly different according to Kaplan-Meier curves (TSP1; 82.5% vs TSP3; 69.2%, log-rank test P = .39). The cumulative incidence rates of remission of hematuria (94.4% vs 85.4%, P = .56) and clinical remission (85.0% vs 64.8%, P = .07) were comparable in both groups, while those of proteinuria showed higher rates in TSP1 than TSP3 (88.4% vs 65.4%, P = .02). The cumulative incidence of relapse of hematuria (5.6% vs 2.3%, P = .42) and proteinuria (7.1% vs 3.3%, P = .41) showed no significant differences in the 2 groups. Cox regression analyses showed that the number of courses of corticosteroid pulse therapy was not significantly associated with renal outcome (TSP1 vs TSP3; Hazard ratios 0.69, 95% confidence intervals 0.29-1.64, P = .39).The effect of single-course corticosteroid pulse therapy is not statistically, significantly different from triple-course in TSP protocol for improving renal outcome and preventing relapse in patients with IgAN. Single-course corticosteroid pulse therapy may become a treatment option for patients with IgAN.

Long-Term Outcome of ABO-Incompatible Kidney Transplantation in Patients Treated With Low-Dose Rituximab Regimen.

BACKGROUND: Introduction of rituximab in the desensitization protocols for ABO-incompatible (ABOI) kidney transplantation (KTX) has afforded excellent results. However, the acceptability of minimal dosage of rituximab in these protocols remains to be defined. METHODS: Sixty-three patients who underwent ABOI KTX were included in this study. The desensitization protocol consisted of plasmapheresis, tacrolimus, mycophenolate mofetil, methylprednisolone, intravenous immunoglobulin, basiliximab, and low-dose rituximab (100 mg/body). We evaluated the efficacy, safety, and long-term outcome of this protocol (group R, n = 39) and compared them with those of patients who underwent splenectomy (group S, n = 24). RESULTS: Graft and patient survival at 10 years after KTX were comparable between the groups (94.4% [group R] vs 95.4% [group S] and 94.6% [group R] vs 95.8% [group S], respectively). The incidence of acute antibody-mediated rejection (AAMR) was similar in the 2 groups (10.2% vs 12.5%). There were no significant differences in the incidence of chronic active antibody-mediated rejection. Of the patients, 7 developed AAMR and 3 of these patients (1 in group R and 2 in group S) lost their grafts. There were no significant differences in the incidence of chronic active antibody-mediated rejection. The incidence of postoperative cytomegalovirus infection in group R was significantly lower than that in group S. Furthermore, the incidence of postoperative late-onset neutropenia was low in group R. CONCLUSIONS: A low-dose rituximab regimen for ABOI KTX is acceptable for preventing AAMR with a low incidence of delayed adverse events.

Clinicopathological characteristics of thrombospondin type 1 domain-containing 7A-associated membranous nephropathy.

Thrombospondin type 1 domain-containing 7A (THSD7A) is a recently identified target antigen of idiopathic membranous nephropathy (iMN). The clinicopathological characteristics of THSD7A-associated MN are poorly characterised due to low prevalence among MN patients. Among 469 consecutive cases of pathologically confirmed MN diagnosed at four centres in Japan, 14 cases were confirmed positive for THSD7A by immunohistochemistry (3.0%). The prevalence of THSD7A-associated MN tended to be higher in northern Japan. Most cases demonstrated nephrotic-range proteinuria (12/14 cases, 86%). In two patients, cancer was detected at the time of renal biopsy (small-cell carcinoma of the lung and prostatic adenocarcinoma with neuroendocrine differentiation). Both tumours were negative for THSD7A. Four patients had concurrent or previous incidence of allergic diseases, including one patient with Kimura's disease. Pathological analysis of kidney biopsy tissue revealed slight mesangial cell proliferation in three cases and spike formation in one case. Immunofluorescence studies demonstrated that IgG subclass was mainly IgG4-dominant/codominant (12/13, 92% cases), while the case with prostatic cancer had an IgG2-dominant distribution. The immunostaining profile for components of the lectin complement pathways was not significant in three cases including two patients with malignancy. One case was dual positive for THSD7A and PLA2R. Of 10 cases with known clinical follow-up data, 6 demonstrated reduced serum creatinine and 8 presented reduced proteinuria. In summary, although the major IgG phenotype was usually IgG4-dominant/codominant, clinical background was otherwise heterogeneous. Further investigation of regional differences in THSD7A-associated MN prevalence may reveal genetic and environmental risk factor and associated pathogenic mechanisms.

A Case of Chronic Calcium Oxalate Nephropathy due to Short Bowel Syndrome and Cholecystectomy.

BACKGROUND: Oxalate nephropathy is a rare disease. Especially chronic oxalate nephropathy still has many unknown aspects as compared to acute oxalate nephropathy with relatively well-known causality. CASE PRESENTATION: The patient was a 70-year-old woman who had a history of small bowel resection 25 years before, cholecystectomy 10 years before, and renal stones (calcium oxalate stones) 7 years before. She had been suffering from chronic diarrhea and had been treated by a local physician. The patient was found to have renal dysfunction (creatinine 3.09 mg/dL, eGFR 12.3 mL/min/1.73 m2, hemoglobin 7.8 g/dL) and was referred to our department. The patient was admitted to our hospital for further investigation. Renal ultrasound showed hepatorenal echo contrast in an opposite manner and clear contrast between the renal cortex and medullary pyramid. Renal biopsy was performed, and histological examination showed tubulointerstitial disorder due to deposition of calcium oxalate. Daily urinary excretion of calcium oxalate was significantly increased. The patient was encouraged to drink water and administered vitamin B6, citric acid, K and Na hydrate. Thereafter, her symptoms improved. CONCLUSION: Case reports of chronic oxalate neuropathy are rare in the literature, and its underlying mechanism has not been understood. Our patient had a history of small bowel resection and cholecystectomy. We considered that her short bowel syndrome had influenced the development of calcium oxalate nephropathy.

Interferon-inducible Mx1 protein is highly expressed in renal tissues from treatment-naïve lupus nephritis, but not in those under immunosuppressive treatment.

OBJECTIVES: The aim of this study was to clarify the consequences of Mx1, one of the IFN-inducible proteins, in the peripheral blood as well as in renal tissues in patients with systemic lupus erythematosus (SLE). PATIENTS AND METHODS: Mx1 protein concentrations in (PBMCs) from 18 SLE patients mostly in their stable disease status, 11 IgA nephropathy (IgAN) patients, 5 ANCA-associated vasculitis (AAV) patients and 16 healthy controls were measured using enzyme-linked immunosorbent assay (ELISA). Mx1 expression in renal specimens from 18 patients with lupus nephritis (LN), 18 with IgAN and 10 with AAV were evaluated using immunohistochemistry. RESULTS: Mx1 protein concentrations in lysates of PBMCs were significantly higher in SLE patients compared with those in other three groups. Mx1-positive area in renal tissues was significantly dominant in both glomeruli and renal tubules of LN compared with other renal diseases. Renal Mx1 protein levels were lower in LN after immunosuppressive treatment, compared with those from immunosuppressant-naïve patients. CONCLUSION: Mx1 levels were upregulated in lupus peripheral blood even when their disease activities were stable. On the other hand, Mx1 was highly expressed in kidneys from patients with LN before treatment, which was decreased after immunosuppressive treatment. These results suggest that Mx1 is a potential marker for the diagnosis of SLE in the peripheral blood and also for the activity of lupus nephritis in the kidney.

Immunohistochemical identification of Propionibacterium acnes in granuloma and inflammatory cells of myocardial tissues obtained from cardiac sarcoidosis patients.

BACKGROUND: Although rare, cardiac sarcoidosis (CS) is potentially fatal. Early diagnosis and intervention are essential, but histopathologic diagnosis is limited. We aimed to detect Propionibacterium acnes, a commonly implicated etiologic agent of sarcoidosis, in myocardial tissues obtained from CS patients. METHODS AND RESULTS: We examined formalin-fixed paraffin-embedded myocardial tissues obtained by surgery or autopsy and endomyocardial biopsy from patients with CS (n = 26; CS-group), myocarditis (n = 15; M-group), or other cardiomyopathies (n = 39; CM-group) using immunohistochemistry (IHC) with a P. acnes-specific monoclonal antibody. We found granulomas in 16 (62%) CS-group samples. Massive (≥14 inflammatory cells) and minimal (<14 inflammatory cells) inflammatory foci, respectively, were detected in 16 (62%) and 11 (42%) of the CS-group samples, 10 (67%) and 10 (67%) of the M-group samples, and 1 (3%) and 18 (46%) of the CM-group samples. P. acnes-positive reactivity in granulomas, massive inflammatory foci, and minimal inflammatory foci were detected in 10 (63%), 10 (63%), and 8 (73%) of the CS-group samples, respectively, and in none of the M-group and CM-group samples. CONCLUSIONS: Frequent identification of P. acnes in sarcoid granulomas of originally aseptic myocardial tissues suggests that this indigenous bacterium causes granuloma in many CS patients. IHC detection of P. acnes in massive or minimal inflammatory foci of myocardial biopsy samples without granulomas may be useful for differentiating sarcoidosis from myocarditis or other cardiomyopathies.

Cytomegalovirus peritonitis after kidney transplantation diagnosed through histopathological examination.

Among organ transplant recipients, cytomegalovirus (CMV) commonly results in various types of infection such as pneumonitis, hepatitis, and enterocolitis. However, CMV peritonitis is very rare and difficult to diagnose owing to lack of visible clinical signs. We present a case of a 35-year-old female kidney recipient who developed abdominal pain and urinary retention caused by CMV peritonitis. To our knowledge, this is the first case report of CMV peritonitis after organ transplantation to be diagnosed through histopathological examination.

Histones and Neutrophil Extracellular Traps Enhance Tubular Necrosis and Remote Organ Injury in Ischemic AKI.

Severe AKI is often associated with multiorgan dysfunction, but the mechanisms of this remote tissue injury are unknown. We hypothesized that renal necroinflammation releases cytotoxic molecules that may cause remote organ damage. In hypoxia-induced tubular epithelial cell necrosis in vitro, histone secretion from ischemic tubular cells primed neutrophils to form neutrophil extracellular traps. These traps induced tubular epithelial cell death and stimulated neutrophil extracellular trap formation in fresh neutrophils. In vivo, ischemia-reperfusion injury in the mouse kidney induced tubular necrosis, which preceded the expansion of localized and circulating neutrophil extracellular traps and the increased expression of inflammatory and injury-related genes. Pretreatment with inhibitors of neutrophil extracellular trap formation reduced kidney injury. Dual inhibition of neutrophil trap formation and tubular cell necrosis had an additive protective effect. Moreover, pretreatment with antihistone IgG suppressed ischemia-induced neutrophil extracellular trap formation and renal injury. Renal ischemic injury also increased the levels of circulating histones, and we detected neutrophil infiltration and TUNEL-positive cells in the lungs, liver, brain, and heart along with neutrophil extracellular trap accumulation in the lungs. Inhibition of neutrophil extracellular trap formation or of circulating histones reduced these effects as well. These data suggest that tubular necrosis and neutrophil extracellular trap formation accelerate kidney damage and remote organ dysfunction through cytokine and histone release and identify novel molecular targets to limit renal necroinflammation and multiorgan failure.

De novo proliferative glomerulonephritis with monoclonal IgG deposits of the IgG1κ subtype in a kidney allograft.

Proliferative glomerulonephritis with monoclonal immunoglobulin G (IgG) deposits (PGNMID) has recently been described in cases with glomerular disease. Only 16 cases of recurrent or de novo PGNMID have been reported in the transplanted kidney. Here we report a case of de novo PGNMID in a renal allograft diagnosed in the early stage by protocol biopsy. A 41-year-old male with end-stage kidney disease caused by focal glomerular sclerosis received a living-related kidney transplant. The post-transplantation course was stable, except for an early episode of acute T cell-mediated rejection. Mesangial C1q deposition was found on the 3-year protocol biopsy. On the 4-year protocol biopsy, mild mesangioproliferative changes and deposition of IgG, C1q, C3, IgG1, and κ light chain were evident, confirming the diagnosis of PGNMID of the IgG1κ subtype. Furthermore, mild proteinuria was detected at that time. Because a subsequent haematological examination revealed high copy number Epstein-Barr virus (EBV) DNA and free κ light chain in blood, the post-transplant lymphoproliferative disorder (PTLD) was suspected. Mycophenolate mofetil (MMF) was discontinued and rituximab was administered for the treatment of PTLD; subsequently, the improvement in proteinuria and serum creatinine was found 2 months after rituximab administration.

Microvascular inflammation in early protocol biopsies of renal allografts in cases of chronic active antibody-mediated rejection.

AIM: Chronic active antibody-mediated rejection (chronic ABMR) is one important cause of late-stage renal allograft loss. However, few reports have used protocol biopsy to observe changes over time in cases that develop chronic ABMR. The aim of this study was to use protocol biopsy to clarify the histological features of cases that develop chronic ABMR. METHODS: We recruited 379 ABO compatible patients who underwent protocol biopsy at our hospital from 2010 to 2014. Seventeen of these patients were diagnosed with chronic ABMR (chronic ABMR group), and 12 patients were class 2 donor-specific antibody (DSA) positive and were not diagnosed with chronic ABMR (class 2 DSA-positive group). With the addition of a control group consisting of 30 DSA negative patients, these three groups were compared for Banff factors in protocol biopsies taken 3 months, 6 months, 1 year, 3 years, and 5 years after the transplant. RESULTS: Three months post transplant, the chronic ABMR group had a significantly higher number of patients exhibiting g + ptc > 0 than that in the control group (P = 0.01). At 1, 3, and 5 years post transplant, significantly more subjects in the chronic ABMR and class 2 DSA-positive groups compared with the control group exhibited g + ptc > 0 (P < 0.03). Five years post transplant, the chronic ABMR group exhibited a significantly higher mean c4d score than that in the control group (P = 0.02). The only significant difference observed between the chronic ABMR group and the class 2 DSA-positive group was in cg scores at 5 years post transplant, which were significantly higher in the chronic ABMR group (P = 0.03). CONCLUSIONS: These results suggest that cases exhibiting microvascular inflammation in the early post-transplant period may develop chronic ABMR, and it would be highly beneficial to perform focused electron microscope surveillance of these cases.

Tacrolimus reduction with everolimus addition for calcineurin inhibitor-induced arteriolopathy in kidney allografts.

AIM: The aim of this study was to evaluate the effect of tacrolimus (TAC) reduction with everolimus (EVR) addition on the maintenance immunosuppression for the recipients with calcineurin inhibitor arteriolopathy (CNIA). METHODS: This retrospective study consisted of 13 kidney allograft recipients who were found to have CNIA on protocol biopsy specimens. The time of intervention was 9-89 months. All the patients were on TAC, mycophenolate mofetil (MMF). 9 of 13 were on steroid. EVR was added and TAC dose was reduced. MMF dose was not changed. Revaluation biopsy was taken 12 months after the intervention. TAC trough levels (TACC0 , ng/mL), EVR trough levels (EVRC0 , ng/mL), estimated glomerular filtration rate (eGFR, mL/min), and urine protein per creatinine (uP/Cr, g/g creatinine) were compared before and 1 year after intervention. Changes in pathological findings and adverse events were also reviewed. RESULTS: Aah scores improved in 5 patients. Aah scores did not change in the rest of the patients. No deterioration was observed. No improvement was seen in those with aah3. TACC0 reduced from 3.3 to 2.3. EVRC0 at revaluation was 4.1. eGFR improved from 44.3 to 49.8. uP/Cr slightly increased from 0.20 to 0.26. EVR was discontinued in 1 patient due to an adverse event. EVR dose was reduced in 5 patients due to adverse events. CONCLUSION: TAC reduction with EVR addition improves CNIA histologically in selected cases.

Decreased expression of thymus-specific proteasome subunit ß5t in Down syndrome patients.

AIMS: The majority of patients with Down syndrome (DS), trisomy 21, have morphologically abnormal thymuses and present with intrinsic immunological abnormalities affecting mainly the cellular immune response. The aim of this study was to examine whether the expression of functionally important molecules is altered in thymic stromal cells in patients with DS. METHODS AND RESULTS: We analysed thymic tissues from patients with trisomy 13 (n = 4), trisomy 18 (n = 14) and trisomy 21 (n = 13) for histological alterations, and for the expression of functionally important molecules such as ß5t, a thymoproteasome subunit, and cathepsins L and S. In patients with trisomy 13 and trisomy 18, the thymus was morphologically normal or showed only mild depletion of cortical thymocytes. In contrast, the thymus showed variable histological changes in patients with trisomy 21; six of 13 cases showed severe depletion of thymocytes accompanied by the disappearance of thymic lobular architecture. In such thymuses, spindle-shaped keratin-positive cells were densely distributed, and expression of ß5t, but not of cathepsin L, was markedly decreased. CONCLUSIONS: The present study suggests that abnormal thymic architecture and decreased expression of functionally important molecules in thymic stromal cells may be involved in immunological abnormalities in DS patients.