Antibodies against fetal muscle proteins in serum from patients with amyotrophic lateral sclerosis.

The serum from 30 patients with amyotrophic lateral sclerosis and 30 controls was tested by immunoblot with protein extracts obtained from fetal muscle, adult muscle, and denervated muscle. Results with adult and denervated muscle confirm previous reports that show a lack of particular reactivity of ALS serum when compared with control serum. However, we found reacting bands 5 times more frequently with ALS than with controls in the immunoblot with protein extract from rat fetal muscle; we confirmed reactivity by immunoperoxidase staining in frozen sections of fetal muscle. Our results point to the possibility of an immune reaction in ALS patients against ephemeral proteins of muscle that are present in large quantities at early stages of muscle differentiation and innervation.