Frequency and significance of anti-glutathione S-transferase autoantibody (anti-GST A1-1) in autoimmune hepatitis

A Comparison of Line Blots, Enzyme-linked Immunosorbent, and RNA-immunoprecipitation Assays of Antisynthetase Antibodies in Serum Samples from 44 Patients

Objective To determine the differences between anti-aminoacyl tRNA synthetase (ARS) antibodies among line blots, enzyme-linked immunosorbent assay (ELISA) anti-ARS tests, and RNA-immunoprecipitation (IP) assays. Methods Sera from patients with confirmed or suspected antisynthetase syndrome (ASS) that were positive for either the anti-ARS test or the line-blot assay were used to perform an RNA-IP assay and ELISA to detect individual anti-ARS antibodies. Results Among the 44 patients, 10 were positive only in line-blot assays, 6 were positive only in the anti-ARS test, and 28 were positive in both assays. We compared the accuracy of these assays against the gold standard RNA-IP assay. The κ coefficient was 0.23 in the line-blot assay, but this increased to 0.75 when the cut-off was increased from 1+ to 2+. The κ coefficient was 0.73 in the anti-ARS test. The κ coefficient was 0.85 for positivity in both assays. Patients with ASS that was positive in an RNA-IP assay more frequently had mechanic's hand (62.1% vs. 20%: p=0.031), myositis (51.7 vs. 10%: p=0.028) and more ASS symptoms than those who were positive only in line-blot assays (3.48 vs. 2.2: p=0.019). Conclusions Clinicians need to understand the features of each assay and determine diagnoses by also considering clinical presentations. Diagnoses should not be judged based only on the results of line-blot assays due to the risk of a misdiagnosis from false positives.

Localization of canine, feline, and mouse renal membrane proteins

Immunohistochemistry allows the localization of proteins to specific regions of the nephron. This article reports the identification and localization of proteins in situ within normal canine, feline, and mouse kidney by immunohistochemistry; maps their distribution; and compares results to previously reported findings in other species. The proteins investigated are aquaporin 1, aquaporin 2, calbindin D-28k, glutathione S-transferase-α, and Tamm-Horsfall protein. Aquaporins are integral membrane proteins involved in water transport across cell membranes. Calbindin D-28k is involved in renal calcium metabolism. Glutathione S-transferase-α is a protein that aids in detoxification and drug metabolism. The role of Tamm-Horsfall protein is not fully understood. Proposed functions include inhibition of calcium crystallization and reduction of bacterial urinary tract infection. The authors' findings in the dog are similar to those in other species: Specifically, the authors localize aquaporin 1 to the proximal convoluted tubule epithelium, vasa recta endothelium, and descending thin limbs; aquaporin 2 to collecting duct epithelium; and calbindin D-28k within distal convoluted tubule epithelium. Glutathione S-transferase-α has variable expression and is found in only the renal transitional epithelium in some individuals, in only the proximal straight tubules in others, or in both locations in others. Tamm-Horsfall protein localizes to thick ascending limb epithelium. These findings are similar in the cat, with the exception that aquaporin 1 is located in glomerular podocytes, in addition to proximal convoluted tubule epithelium, and glutathione S-transferase-α is found solely within the proximal convoluted tubule within all kidney samples examined. The mouse kidney is almost identical to the dog but expresses glutathione S-transferase-α in the glomeruli only.

Primary biliary cirrhosis: What do autoantibodies tell us?

Primary biliary cirrhosis (PBC) is a chronic, progressive, cholestatic, organ-specific autoimmune disease of unknown etiology. It predominantly affects middle-aged women, and is characterized by autoimmune-mediated destruction of small- and medium-size intrahepatic bile ducts, portal inflammation and progressive scarring, which without proper treatment can ultimately lead to fibrosis and hepatic failure. Serum autoantibodies are crucial tools for differential diagnosis of PBC. While it is currently accepted that antimitochondrial antibodies are the most important serological markers of PBC, during the last five decades more than sixty autoantibodies have been explored in these patients, some of which had previously been thought to be specific for other autoimmune diseases.

Autoantibodies to glutathione S-transferase theta 1 in patients with primary sclerosing cholangitis and other autoimmune diseases

Primary sclerosing cholangitis (PSC) is an enigmatic disorder with a suggested autoimmune basis. A variety of autoantigens have been suggested but no specific or highly directed epitope has been identified. To address this issue, we constructed a cDNA library from normal human choledochus and screened expressing clones with serum from a patient with PSC and inflammatory bowel disease (IBD). Based on this screening, glutathione S-transferase theta 1 (GSTT1) was identified as a potential autoantigenic target. To study the specificity of GSTT1, we determined immunoreactivity using a panel of 58 patients with PSC, with and without IBD, 57 patients with IBD, 31 patients with Hashimoto's thyroiditis, 30 patients with primary biliary cirrhosis (PBC), 20 patients with insulin dependent diabetes mellitus, 22 patients with autoimmune polyendocrine syndrome type I, 10 patients with systemic lupus erythematosus (SLE), 20 patients with Sjögren's syndrome, 12 patients with autoimmune pancreatitis, 28 patients with Addison's disease, 27 patients with Grave's disease, 17 with myasthenia gravis, and 118 healthy controls. Reactivity against GSTT1 was found with PSC and IBD as well as some patients with other autoimmune pathology, indicating that this population of antibodies is neither specific nor a sensitive serologic marker for PSC, but the frequency was clearly higher in autoimmune patients than controls. GSTT1-antibodies have been described in persons with GSTT1-null genotype and are suggested to develop as an alloimmune response to blood transfusions from GSTT1-positive donors or pregnancies with GSTT1-positive children. Therefore, two IBD patients with and 15 PSC patients without GSTT1-antibodies were genotyped for GSTT1 to investigate if the presence of GSTT1-antibodies was associated with the GSTT1-null genotype and possibly caused by an alloimmune response. Both IBD patients and three of the PSC patients were of the GSTT1-null genotype. We note that the frequency of GSTT1-antibodies in this study is more than 100-fold higher than the frequency described earlier in patients with autoimmune diseases. We also observe an increased frequency of GSTT1-antibodies in patients with autoimmune diseases compared to healthy controls. This increased frequency can be explained by an autoimmune phenotype which increases susceptibility to such autoantibodies, or by a high frequency of the GSTT1-null genotype in autoimmune disease.

Localization of CYP4B1 in the rat nasal cavity and analysis of CYPs as secreted proteins

CYP4B1 is highly expressed in rat nasal respiratory mucosa, and to a lesser extent in olfactory mucosa. Examination of high-power photomicrographs suggests that CYP4B1 may be a secreted protein, based on the fact that immunoreactivity appears to be present in the lumens of ducts of Bowman's glands (rather than intracellular localization, as we observed with an antibody recognizing CYP2F4) and in secretory granules in respiratory mucosa. Furthermore, anti-CYP4B1 immunoreactivity is present on the surface of both respiratory and olfactory mucosa. We used SignalP 3.0 analysis to ascertain the likelihood that rat CYP4B1 is a secreted protein. While this analysis does not suggest that rat CYP4B1 is a secreted protein, several other cytochrome P450 enzymes were predicted to be secreted proteins. The observation that multiple human cytochrome P450s appear to be secreted proteins helps to explain the appearance of anti-cytochrome P450 antigens in cases of human autoimmune liver diseases.

Antibodies against glutathione S-transferase T1 (GSTT1) in patients with GSTT1 null genotype as prognostic marker: long-term follow-up after liver transplantation

An objective to improve the evolution of transplants is to identify risk biomarkers of morbidity and loss of allograft. In liver transplant (LTX) recipients, an association has been demonstrated between the presence of mismatch for glutathione S-transferase T1 (GSTT1) and the development of de novo immune hepatitis (IH). In 419 LTX patients we analyzed, for a period of 1 to 14 years, the development of "atypical" autoantibodies directed against GSTT1 and their relationship with the mismatch for GSTT1 genotype and with the risk for developing de novo IH. A total of 6.9% LTX recipients had "atypical" autoantibodies and 24 showed mismatch (recipient/donor) for GSTT1 genotype. From this last group, up to 70% developed de novo IH and graft dysfunction after LTX (95% confidence interval: 17.4-37.5 months). In LTX recipients with a GSTT1 null genotype, the evaluation of "atypical" autoantibodies is useful for monitoring the development of de novo IH.