Expression of CD43 in human microglia and its downregulation in Alzheimer's disease

Area of Science:

• Neuroscience
• Immunology
• Cell Biology

Background:

• CD43 (leukosialin, sialophorin) is a transmembrane protein expressed on various immune cells.
• Microglia are the resident immune cells of the brain and play critical roles in neuroinflammation.
• Alzheimer disease (AD) is characterized by neuroinflammation and microglial activation.

Purpose of the Study:

• To investigate the expression of CD43 in the brain tissue of neurologically normal individuals and patients with Alzheimer disease.
• To compare CD43 expression levels in microglia between normal and AD brains.
• To explore the potential role of CD43 in microglial activation and function.

Main Methods:

• Immunohistochemical analysis of brain tissue from normal and AD cases.
• Detection and quantification of CD43 immunoreactivity in microglia and other brain cells.
• Comparison of CD43 expression with HLA-DR, a marker of microglial activation.

Main Results:

• Abundant CD43 immunoreactivity was observed in ramified microglia of normal brain tissue.
• CD43 expression was markedly lower in microglia from AD brains compared to control brains.
• In contrast to CD43, HLA-DR expression was significantly upregulated in AD microglia, indicating activation.

Conclusions:

• CD43 is expressed at higher levels in resting or ramified microglia compared to activated microglia.
• This finding suggests CD43 may have an anti-adhesional role in microglia, with its expression decreasing upon activation.
• CD43 represents a novel microglial marker associated with the resting state, offering insights into microglial dynamics in neurodegenerative diseases.