In addition, CD8 + T-cells have been shown to injure neurons and transect axons in vitro (Medana et al., 2000 (Medana et al., , 2001 , and imaging studies have indicated that axonal loss in MS is a direct correlate for disability (Narayanan et al., 1997; Truyen et al., 1996; van Waesberghe et al., 1999) .