The four lesion types are demonstrated: (A and B) active???characterized by increased infiltration of inflammatory cells (HLA-DR/LN3) and a loss of myelin staining (LFB), associated with a decrease in axonal staining; (C and D) chronic-active???showed an expanding border of HLA-DR+ve inflammatory cells and a demyelinated core with significant reduction in axon staining; (E and F) chronic inactive?