IgG1 protects against renal disease in a mouse model of cryoglobulinaemia.

Immunoglobulins protect against disease to a considerable extent by activating complement and stimulatory immunoglobulin crystallizable fragment receptors (Ig FcRs), and aggregating microbial pathogens. Yet IgG1, the predominant murine serum Ig isotype, cannot activate complement by the classical pathway, binds more avidly to an inhibitory than to stimulatory FcRs, and has limited ability to aggregate pathogens. In these regards, it resembles human IgG4 (ref. 4). We hypothesized that limited ability to activate effector mechanisms might protect against immune complex immunopathology. Here we show that IgG1-deficient (γ1(-)) mice, immunized with a potent antigen, develop lethal renal disease soon after they begin to produce antigen-specific antibody, whereas similarly immunized wild-type mice remain healthy. Surprisingly, renal disease in this model is complement and FcR independent and results from immune complex precipitation in glomerular capillaries, as in some cryoglobulinaemic humans. IgG3, which self-associates to form large immune complexes, accounts for more than 97% of the mouse Ig in this cryoglobulin; furthermore, glomerular disease develops when mice are injected with IgG3 anti-trinitrophenyl (TNP) monoclonal antibody followed by a TNP-labelled protein. Renal disease is prevented in both active and passive immunization models by antigen-specific IgG1; other isotypes are less potent at preventing disease. These observations demonstrate the adaptive significance of Ig isotypes that poorly activate effector mechanisms, reveal an immune-complex-dependent, complement- and FcR-independent nephrotoxic mechanism, and suggest that isotypes that poorly activate effector mechanisms may be useful for inhibiting immune complex immunopathology.

Genetic variants in acute, acute recurrent and chronic pancreatitis affect the progression of disease in children.

BACKGROUND/OBJECTIVES: Acute pancreatitis (AP) is emerging in pediatrics. A subset of children with AP progresses to acute recurrent pancreatitis (ARP) and chronic pancreatitis (CP). The role of extensive gene testing in the progression has not been investigated previously. We have followed children enrolled in the registry and at our center for progression to ARP and CP after the first attack. METHODS: This study utilizes an extensive gene sequencing panel as a platform to evaluate the role of genetics in first attack AP, and the progression over time, from first attack to ARP and CP in children. RESULTS: Genes, with corresponding variants were involved in the 3 groups studied: AP, ARP and CP. We have shown that the presence of gene variants from the eight tested genes is enriched in the CP group compared to the AP and ARP groups. The presence of more than one gene was associated with CP (p = 0.01). SPINK1 mutation(s) was significantly associated with faster progression to ARP, (p = 0.04). Having a variant from CFTR, SPINK1 or PRSS1, was associated with the faster progression from AP to CP over time (p < 0.05). CONCLUSIONS: This study shows that genetics have a significant role in progression to ARP and CP from the first attack of pancreatitis.

The 253-kb inversion and deep intronic mutations in UNC13D are present in North American patients with familial hemophagocytic lymphohistiocytosis 3.

BACKGROUND: The mutations in UNC13D are responsible for familial hemophagocytic lymphohistiocytosis (FHL) type 3. A 253-kb inversion and two deep intronic mutations, c.118-308C > T and c.118-307G > A, in UNC13D were recently reported in European and Asian FHL3 patients. We sought to determine the prevalence of these three non-coding mutations in North American FHL patients and evaluate the significance of examining these new mutations in genetic testing. PROCEDURE: We performed DNA sequencing of UNC13D and targeted analysis of these three mutations in 1,709 North American patients with a suspected clinical diagnosis of hemophagocytic lymphohistiocytosis (HLH). RESULTS: The 253-kb inversion, intronic mutations c.118-308C > T and c.118-307G > A were found in 11, 15, and 4 patients, respectively, in which the genetic basis (bi-allelic mutations) explained 25 additional patients. Taken together with previously diagnosed FHL3 patients in our HLH patient registry, these three non-coding mutations were found in 31.6% (25/79) of the FHL3 patients. The 253-kb inversion, c.118-308C > T and c.118-307G > A accounted for 7.0%, 8.9%, and 1.3% of mutant alleles, respectively. Significantly, eight novel mutations in UNC13D are being reported in this study. To further evaluate the expression level of the newly reported intronic mutation c.118-307G > A, reverse transcription PCR and Western blot analysis revealed a significant reduction of both RNA and protein levels suggesting that the c.118-307G > A mutation affects transcription. CONCLUSIONS: These specified non-coding mutations were found in a significant number of North American patients and inclusion of them in mutation analysis will improve the molecular diagnosis of FHL3.

Proteomic profiling of L-cysteine induced selenite resistance in Enterobacter sp. YSU.

BACKGROUND: Enterobacter sp. YSU is resistant to several different heavy metal salts, including selenite. A previous study using M-9 minimal medium showed that when the selenite concentration was 100,000 times higher than the sulfate concentration, selenite entered Escherichia coli cells using two pathways: a specific and a non-specific pathway. In the specific pathway, selenite entered the cells through a yet to be characterized channel dedicated for selenite. In the non-specific pathway, selenite entered the cells through a sulfate permease channel. Addition of L-cystine, an L-cysteine dimer, appeared to indirectly decrease selenite import into the cell through the non-specific pathway. However, it did not affect the level of selenite transport into the cell through the specific pathway. RESULTS: Growth curves using M-9 minimal medium containing 40 mM selenite and 1 mM sulfate showed that Enterobacter sp. YSU grew when L-cysteine was present but died when it was absent. Differential protein expression analysis by two dimensional gel electrophoresis showed that CysK was present in cultures containing selenite and lacking L-cysteine but absent in cultures containing both selenite and L-cysteine. Additional RT-PCR studies demonstrated that transcripts for the sulfate permease genes, cysA, cysT and cysW, were down-regulated in the presence of L-cysteine. CONCLUSION: L-cysteine appeared to confer selenite resistance upon Enterobacter sp. YSU by decreasing the level of selenite transport into the cell through the non-specific pathway.

MHC class I-specific antibody binding to nonhematopoietic cells drives complement activation to induce transfusion-related acute lung injury in mice.

Transfusion-related acute lung injury (TRALI), a form of noncardiogenic pulmonary edema that develops during or within 6 h after a blood transfusion, is the most frequent cause of transfusion-associated death in the United States. Because development of TRALI is associated with donor antibodies (Abs) reactive with recipient major histocompatibility complex (MHC), a mouse model has been studied in which TRALI-like disease is caused by injecting mice with anti-MHC class I monoclonal Ab (mAb). Previous publications with this model have concluded that disease is caused by FcR-dependent activation of neutrophils and platelets, with production of reactive oxygen species that damage pulmonary vascular endothelium. In this study, we confirm the role of reactive oxygen species in the pathogenesis of this mouse model of TRALI and show ultrastructural evidence of pulmonary vascular injury within 5 min of anti-MHC class I mAb injection. However, we demonstrate that disease induction in this model involves macrophages rather than neutrophils or platelets, activation of complement and production of C5a rather than activation of FcγRI, FcγRIII, or FcγRIV, and binding of anti-MHC class I mAb to non-BM-derived cells such as pulmonary vascular endothelium. These observations have important implications for the prevention and treatment of TRALI.