Amyotrophic lateral sclerosis (ALS) is a devastating systemic atrophy affecting the upper and
lower motor neurons. The etiology is unknown, but one theory of pathogenesis supposes
that the motor system is affected by abnormal immune responses. We have studied the
prevalence and extent of lymphocytic infiltration, previously reported as a rare finding in the
ALS spinal cord. Application of monoclonal antibodies against macrophages, T—and B—
cells to spinal cords from 48 ALS patients disclosed a cellular mononuclear infiltrate in 38 …