Transferrin localizes in Bunina bodies in amyotrophic lateral sclerosis

Transferrin, an iron-binding protein, plays an important role in the transport and delivery of circulating ferric iron to the tissues. Amyotrophic lateral sclerosis (ALS) is characterized by the presence of Bunina bodies, skein-like inclusions, Lewy body-like inclusions/round inclusions, and basophilic inclusions in the remaining anterior horn cells in the spinal cord. We examined transverse paraffin sections of lumbar spinal cords from 12 ALS cases including two ALS with dementia and two ALS with basophilic inclusions, using antibodies to human transferrin. The results demonstrated that transferrin localized in Bunina bodies and some of the basophilic inclusions. In contrast, skein-like inclusions and Lewy body-like inclusions or round inclusions did not show obviously detectable transferrin immunoreactivities. Our findings suggest that although the mechanisms underlying transferrin accumulation in Bunina bodies and basophilic inclusions are unknown, transferrin could be involved in forming these inclusions. Furthermore, following cystatin C, transferrin is the second protein that localizes in the Bunina bodies.