Studies on unfolded β2-microglobulin at C-terminal in dialysis-related amyloidosis

Studies on unfolded β 2 -microglobulin at C-terminal in dialysis-related amyloidosis. Background In 1997, Stoppini et al reported that monoclonal antibody specific to the C-terminal 92–99 of β 2 -microglobulin (β 2 m) had been capable of inhibiting fibrillogenesis of β 2 m in vitro. Meanwhile, recent studies have indicated that an acidifying procedure can unfold conformation of the precursor protein, leading to fibril formation of β 2 m as well as a transthyretin. Methods We thus prepared monoclonal antibody specific to the C-terminal 92–99 (mAb 92–99), and investigated its reactivity in plasma ultrafiltrate and amyloid tissues from 18 hemodialysis patients with dialysis-related amyloidosis (DRA). Results β 2 m extracted from ultrafiltrate showed no reaction for mAb 92–99, whereas acidified β 2 m from ultrafiltrate showed a reaction for mAb 92–99. Similarly, a homogenate of carpal amyloid tissues showed a strong reaction for mAb 92–99 on immunoblotting. Immunohistochemical study showed also a distinct staining for mAb 92–99 in 7 Congophilic specimens from DRA patients. More interestingly, staining for mAb 92–99 could be found in most, though not all, non-Congophilic tissues. Conclusion This study demonstrates that the monoclonal antibody specific to the C-terminal 92–99 of β 2 m can detect the conformational intermediate in amyloidogenesis of β 2 m ex vivo, and demonstrates that an unfolded β 2 m at C-terminal could be found not only in Congophilic area but even in non-Congophilic area as well.