Abstract
We have identified two sera containing anti-liver/kidney microsome (anti-LKM) 1 antibody and 7 sera containing anti-Is antibody among one hundred sixty seven samples taken from patients suspected of having autoimmune hepatic diseases. In this study, we report on the immunological characterization of these two antibodies in relation to each other and to the various antimitochondrial antibodies.
Anti-Is antibody was found to be distinct from any of the previously defined antibodies such as anti-LKM 1, anti-MM, precipitating antimitochondrial antibodies (anti-M-A, anti-M-B, anti-M-C and anti-M-D) when tested by double immunodiffusion using rat liver sonicated mitochondrial and microsomal fractions. Anti-Is and anti-LKM 1 were also found to be different in terms of cellular specificity. When viewed by indirect immunofluorescence, anti-LKM 1 significantly stained proximal tubular cells, hepatocytes, and portal area cells, while anti-Is only slightly stained tubular cells. Furthermore, anti-Is antibody was found to be mostly associated with AMA, while anti-LKM 1 was not. Finally, a monospecific anti-Is antibody immunoprecipitated a complex of 87 kd, 80 kd and 72 kd proteins using 35S-methionine labeled HeLa cell extract. The molecular weight of the LKM 1 antigen was estimated to be 50 kd by western blot under reducing conditions using partially purified rat liver microsomal fraction. Clinical characterization of these antibodies has yet to be conducted.
