ANTIACETYLCHOLINE RECEPTOR (ACHR) ANTIBODIES MEASUREMENT IN MYASTHENIA-GRAVIS - THE USE OF CELL-LINE TE671 AS A SOURCE OF ACHR ANTIGEN

Acetylcholine receptor (AChR) from the human rhabdomyosarcoma cell lin e TE671 was compared with that of human ischaemic muscle AChR as a sou rce of the antigen for the diagnosis of myasthenia gravis (MG). The se ra, which were anti-TE671 cell AChR antibody-negative, all came from p atients with low anti-human muscle AChR antibody titers. None of the s era that were seronegative as a result of the human muscle AChR RIA be came positive with TE671 cell AChR. The overall sensitivity was 7% les s using TE671 cell AChR. The lower sensitivity was observed irrespecti ve of the clinical form of MG. It also appeared from this study that e pitopes specific to the junctional isoform of human AChR are essential for the detection of low antibody titers, which accounts for this fea ture, since TE671 cells only express the extrajunctional isoform of AC hR in the surface membrane. Accordingly, AChR from cell line TE671 can not replace human muscle AChR in the conventional diagnostic immunopre cipitation RIA. There are, however, many other useful implications of AChR from cell line TE671.