Demonstrating immune-related antigens in Alzheimer's disease brain tissue

Immune system associated markers have recently been reported in Alzheimer's disease (AD) brain. However, previous studies have not consistently revealed these antigens in the central nervous system. Immunohistochemistry of HLA-DR and other immune antigens (e.g., CD4+, IL-2R) in AD cortical tissue was compared using paraformaldehyde-fixed versus snap-frozen unfixed tissue. In addition, a free-floating immunohistochemistry method was contrasted with an on slide procedure. Even with an HLA-DR antibody known to work well on fixed tissue, unfixed tissue gave superior results. Free-floating immunohistochemistry also increased sensitivity. Where morphologic considerations are paramount, brief fixation with free-floating methods provides a reasonable alternative.