Immunological studies in myotonic dystrophy

Abnormalities of cellular and humoral immunity have been recognised in myotonic dystrophy but their significance is uncertain. To throw further light on this, a group of 22 patients with myotonic dystrophy was investigated, looking specifically for evidence of abnormalities of B lymphocyte function and of disturbed immunoregulation. The previously reported reduction in serum IgG levels was confirmed and, in addition, serum IgA levels were significantly reduced. Autoantibodies to muscle and non-muscle antigens were not found and there was no increase in autoimmune disease or malignancy, suggesting that immunoregulatory mechanisms are not disturbed. The proportions of T and B cells were not significantly different in patients and controls. B-lymphocyte capping with FITC- antihuman IgG was quantitatively altered, the percentage of capped cells after incubation being reduced and the time-course of the capping process being apparently prolonged in the myotonic dystrophy subjects. While there are a number of possible explanations for these findings, they may reflect an intrinsic abnormality of the lymphocyte membrane. This could be part of a more generalised membrane defect which has been suggested to underlie the myotonia and certain other manifestations of this multisystemic disorder.