Immunofluorescence staining and immunological studies of arylsulphatase a of multiple sulphatase deficiency (MSD) and metachromatic leukodystrophy (MLD) fibroblasts

Multiple sulphatase deficiency (MSD) and metachromatic leukodystrophy (MLD) are both characterized by a deficiency of arylsulphatase A (ARS A) activity, although they are inherited as separate autosomal recessive traits. However, it has been found that the immunologically active substance with anti‐ARS A antibody is present in quite normal levels in MLD and in smaller quantities in MSD fibroblasts (Fiddler, 1979). Indirect immunofluorescence staining with anti‐ARS A antibody displayed a coarse granular and diffuse distribution of ARS A or cross‐reacting material (CRM) in the normal control and MLD fibroblasts, whereas very weak fluorescence staining was observed in MSD fibroblasts proportional to the decrease in the ARS A activity observed in the lysate enzyme assay. These results suggest that ARS A deficiency in MLD cells is due to an enzymatically deficient ARS A molecule, which is immunologically cross‐reactive with anti‐normal ARS A antibody. ARS A deficiency in MSD cells appears to be due to a reduced amount of normal ARS A.