Two-dimensional analysis of qualitative and quantitative changes in blood cell proteins in Alzheimer's disease: search for extraneuronal markers.

Numerous abnormalities have been reported to exist in tissues outside the central nervous system in Alzheimer's disease (AD), supporting the conception of the illness as a systemic disorder. Two-dimensional (2-D) polyacrylamide gel electrophoresis with an immobilized pH gradient of 4-8 in the first dimension combined with computer-assisted image analysis was applied in investigation of extraneuronal proteins of blood cell origin in AD to search for extraneuronal markers. No qualitative protein changes specific for the condition could be observed. However, many statistically significant quantitative alterations were detected when AD and control 2-D patterns of extracts prepared from red blood cell membranes, platelets and lymphocytes were compared. One of these spots, with a marked change in mean intensity value, was identified as actin. The concentration of this protein was significantly reduced in AD platelets and lymphocytes.