A novel IgM class autoantibody to a hepatocyte-related 190 kDa molecule in patients with type 1 autoimmune hepatitis

Abstract

It has been reported that autoantibodies to hepatocytes are frequently found in patients with autoimmune hepatitis (AIH). To elucidate the nature of these hepatocyte-specific autoantibodies, we attempted to generate a hepatocyte-specific monoclonal antibody (MoAb) from Epstein-Barr virus-transformed peripheral blood mononuclear cells obtained from a patient with AIH. We established a single clone, 2E3, that continued to produce an immunoglobulin M (IgM) antibody ( -type). This MoAb had the following properties: it reacted mainly with hepatocyte-derived cell lines, rather than with other cell lines, and it reacted with liver tissue but not with other tissues. By immunoblot analysis, we found that this MoAb recognized a 190 kDa molecule on hepatocytes. The MoAb was able to kill hepatocyte-derived cell lines in the presence of fresh human serum. This cytotoxic effect was completely abrogated by heat inactivation of human serum prior to its addition to cell lines. In addition, an IgM autoantibody that recognized a 190 kDa molecule was also found in patients with AIH but not in those with chronic hepatitis C; its titer correlated significantly with serum alanine aminotransferase (ALT) levels in patients with AIH. In conclusion, we generated a human MoAb that recognizes a 190 kDa molecule on hepatocytes. Because of its ability to mediate complement-dependent cytotoxicity and the presence of similar IgM autoantibody in patients with AIH, we hypothesize this autoantibody may play a role in the immunopathogenesis of AIH. (HEPATOLOGY 2004;40:687-692.)

A murine model of acute liver injury induced by human monoclonal autoantibody

“…18 This clone continuously produces IgM (␥-type)-class hepatocyte-specific MoAb. 15 We purified MoAb in a culture supernatant of this clone by using Hitrap IgM purification (Amersham Pharmacia Biotech AB, Uppsala, Sweden) according to the manufacturer's instructions. Contaminating endotoxin in these samples was further removed using Detoxi-Gel (Pierce Co., Rockford, IL).…”

“…15 This MoAb recognized a 190-kd molecule on the hepatocyte membrane and was able to kill human hepatocyte cell lines in a complementdependent manner. In addition, a similar 190-kd molecule-recognizing immunoglobulin M (IgM) autoantibody was also found in AIH patients, and its titer was Abbreviations: Ig, immunoglobulin; AIH, autoimmune hepatitis; MoAb, monoclonal autoantibody; MP, myeloma protein; TBS, C3, complement component 3; AST, asparate aminotransferase; ALT, alanine aminotransferase.…”

Of mice and women: Toward a mouse model of autoimmune hepatitis

“…29 The work is an extension of their recent studies on the generation of a human IgM ( -type) monoclonal antibody (MoAb) by Epstein-Barr virus (EBV) transformation of peripheral blood mononuclear cells from a Japanese patient with type 1 AIH. 30 The MoAb recognises a liver-specific 190 kDa molecule expressed on the surfaces of hepatocytes and could induce complement-dependent lysis of a hepatocyte-derived (HuH2) cell line. 30 In that report, they also documented the detection of circulating IgM (but not IgG) antibodies reacting with the 190 kDa antigen (affinity-purified using the MoAb) in patients with AIH but not in healthy subjects or patients with chronic hepatitis C. Furthermore, titres of the anti-190 kDa IgM antibodies correlated with serum aminotransferase levels in the AIH patients.…”

“…30 The MoAb recognises a liver-specific 190 kDa molecule expressed on the surfaces of hepatocytes and could induce complement-dependent lysis of a hepatocyte-derived (HuH2) cell line. 30 In that report, they also documented the detection of circulating IgM (but not IgG) antibodies reacting with the 190 kDa antigen (affinity-purified using the MoAb) in patients with AIH but not in healthy subjects or patients with chronic hepatitis C. Furthermore, titres of the anti-190 kDa IgM antibodies correlated with serum aminotransferase levels in the AIH patients. In the present study, the authors show that the MoAb also reacts with a 190 kDa molecule on mouse hepatocytes, indicating that this target antigen is both liver-specific and species cross-reactive.…”

“…29,30 It will be interesting to know the identity of this 190 kDa molecule, why it is preferentially expressed on perivenular hepatocytes, why there does not appear to be a class switch from an IgM to an IgG response to it in AIH patients, and whether mice injected with their MoAb develop chronic hepatitis over a longer period of observation. …”