Systemic membrane defect and the inhibition of lymphocyte capping in Duchenne muscular dystrophy

Eight reversible inhibitors were used to study decreases in lymphocyte capping in patients with Duchenne Muscular Dystrophy (DMD) when compared to controls. The inhibitors included hydrocortisone, chlorpromazine, calcium ionophore, Cytochalasin D, propranolol, dibucaine, fluoride and azide. All of these inhibitors disrupt cap formation. Mononuclear leukocytes from DMD patients and controls were isolated from whole blood, incubated with fluorescein-conjugated polyvalent antisera and inhibitor, induced to form caps, and the caps counted using a fluorescent microscope. Cell viabilities and morphology were assessed. After removal of inhibitor, the cells were recounted. All of the inhibitors significantly lowered capping in controls (p less than 0.001), but this effect was seen with only four out of the eight inhibitors in DMD patients. Dibucaine and azide were less inhibitory in patients (p less than 0.005, p greater than 0.05, and p greater than 0.05 respectively) while capping in patients was not inhibited by fluoride and hydrocortisone (p greater than 0.5). The lack of hydrocortisone inhibition suggests that the differences in capping between DMD patients and controls may lie within the membrane itself, rather than its associated components (i.e. cytoskeletal network), and that the defect occurs toward the beginning of the capping sequence.