Improved radioassay of anti-acetylcholine receptor antibody: application for the detection of extremely low antibody titers in sera from patients with myasthenia gravis.
We examined sera from 113 patients with myasthenia gravis (MG). Most of the patients with ocular MG without thymoma and 15% of the patients with generalized MG had immunoprecipitation (IP) titers of anti-acetylcholine receptor (anti-AChR) antibodies within the normal range for healthy subjects. We developed a highly sensitive radioassay using Staphylococcus aureus cells, and re-examined the 86 serum samples that had negative titers by IP. Using the radioassay, we detected anti-AChR antibodies in 27 (31%) of these myasthenic sera, of which 19 were from ocular MG patients without thymoma. By combining the standard IP assay and our new radioassay, we increased to 50% the overall percent positivity of detecting nonblocking-type antibodies in ocular MG patients without thymoma. We detected no anti-AChR antibodies in nearly all patients with various immunological and neurological diseases other than MG, and in all the healthy controls. The data for these sera indicate that in some cases the standard IP assay gives false-negative reactions. Thus, use of the more sensitive radioassay is preferable for accuracy.
Ohta
M
M
Clinical Research Center, Utano National Hospital, Kyoto, Japan.
Ohta
K
K
Mori
F
F
Itoh
N
N
Nishitani
H
H
Hayashi
K
K
D000109:Acetylcholine / Q000037:antagonists & inhibitors; D000906:Antibodies / Q000032:analysis*; D005188:False Negative Reactions; D006801:Humans; D009157:Myasthenia Gravis / Q000276:immunology*; D011863:Radioimmunoassay; D011950:Receptors, Cholinergic / Q000276:immunology*; D013211:Staphylococcus aureus
D000906:Antibodies; D011950:Receptors, Cholinergic; D000109:Acetylcholine