Correlation between the expression of DNA topoisomerases I and IIalpha and clinical parameters in kidney disease

Autoantibodies against DNA topoisomerase I promote renal allograft rejection by increasing alloreactive T cell responses

Antibodies reactive to self-antigens are an important component of posttransplant immune responses. The generation requirements and functions of autoantibodies, as well as the mechanisms of their influence on alloimmune responses, still remain to be determined. Our study investigated the contribution of autoimmunity during rejection of renal allografts. We have previously characterized a mouse model in which the acute rejection of a life-supporting kidney allograft is mediated by antibodies. At rejection, recipient sera screening against >4000 potential autoantigens revealed DNA topoisomerase I peptide 205-219 (TI-I205-219) as the most prominent epitope. Subsequent analysis showed TI-I205-219-reactive autoantibodies are induced in nonsensitized recipients of major histocompatibility complex-mismatched kidney allografts in a T cell-dependent manner. Immunization with TI-I205-219 broke self-tolerance, elicited TI-I205-219 immunoglobin G autoantibodies, and resulted in acute rejection of allogeneic but not syngeneic renal transplants. The graft loss was associated with increased priming of donor-reactive T cells but not with donor-specific alloantibodies elevation. Similarly, passive transfer of anti-TI-I205-219 sera following transplantation increased donor-reactive T cell activation with minimal effects on donor-specific alloantibody levels. The results identify DNA topoisomerase I as a novel self-antigen in transplant settings and demonstrate that autoantibodies enhance activation of donor-reactive T cells following renal transplantation.

Network analysis of genes regulated in renal diseases: implications for a molecular-based classification

Background

Chronic renal diseases are currently classified based on morphological similarities such as whether they produce predominantly inflammatory or non-inflammatory responses. However, such classifications do not reliably predict the course of the disease and its response to therapy. In contrast, recent studies in diseases such as breast cancer suggest that a classification which includes molecular information could lead to more accurate diagnoses and prediction of treatment response. This article describes how we extracted gene expression profiles from biopsies of patients with chronic renal diseases, and used network visualizations and associated quantitative measures to rapidly analyze similarities and differences between the diseases.

Results

The analysis revealed three main regularities: (1) Many genes associated with a single disease, and fewer genes associated with many diseases. (2) Unexpected combinations of renal diseases that share relatively large numbers of genes. (3) Uniform concordance in the regulation of all genes in the network.

Conclusion

The overall results suggest the need to define a molecular-based classification of renal diseases, in addition to hypotheses for the unexpected patterns of shared genes and the uniformity in gene concordance. Furthermore, the results demonstrate the utility of network analyses to rapidly understand complex relationships between diseases and regulated genes.

Fever of unknown origin secondary to type I crescentic glomerulonephritis and anti-SCl 70 antibodies without clinical manifestations of systemic sclerosis

A 57-year-old woman presented with fever and cellulitis of the right leg. Urinalysis and kidney function were normal on admission. Cellulitis remitted but fever persisted for six weeks. X-ray imaging, cultures, serological assays for viruses and autoimmunity did not reveal the cause of fever. Unexpectedly anti-Scl 70 (anti-topoisomerase I) antibodies were positive. A skin biopsy ruled out scleroderma. On the fifth hospitalization week kidney function declined in association with hematuria, leucocyturia, and proteinuria. Prednisone was administered due to clinical suspicion of drug-induced interstitial nephritis. Fever declined in 24 h, but renal failure became rapidly worse requiring hemodialysis. Kidney biopsy revealed extensive crescentic glomerulonephritis (CGN), with much glomerular destruction, with an IgG-positive linear pattern on immunofluorescence microscopy. No overtly active microangiopathy or vasculitis were present. There was no pulmonary involvement and anti-glomerular basement membrane antibodies were not detected in the serum. After one year anti-Scl 70 antibodies were still positive without scleroderma manifestations and 17 months later the patient received a kidney transplant with excellent results. Presentation of type 1 CGN as a fever of unknown origin (FUO) is exceptional. Anti-Scl 70 antibodies are highly specific for scleroderma and are seldom present in other diseases. As far as we are aware there are no published cases of the association of type 1 CGN with anti-Scl 70 antibodies.

Type IA topoisomerases: a simple puzzle?

Type IA topoisomerases are enzymes that can modify DNA topology. They form a distinct family of proteins present in all domains of life, from bacteria to archaea and higher eukaryotes. They are composed of two domains: a core domain containing all the conserved motifs involved in the trans-esterification reactions, and a carboxyl-terminal domain that is highly variable in size and sequence. The latter appears to interact with other proteins, defining the physiological use of the topoisomerase activity. The evolutionary relevance of this topoisomerase-cofactor complex, also known as the "toposome", as well as its enzymatic consequences are discussed in this review.