Interplay between CD33 and TREM2 in Alzheimer's Disease: Potential Mechanistic Insights into Microglial Function in Amyloid Pathology.

Alzheimer's disease (AD) is a prevalent neurodegenerative disorder characterized by the accumulation of amyloid-β (Aβ) plaques, tau neurofibrillary tangles, and progressive neuronal loss leading to cognitive decline. With millions affected worldwide, there remains an urgent need for innovative treatment strategies to combat this disease. Genome-wide association studies (GWAS) have identified genes expressed in microglia, the resident immune cells of the brain, as key mediators of AD susceptibility. Among microglial risk genes, CD33 and TREM2 stand out for their contrasting roles in AD risk. Accumulating evidence indicates that these receptors converge on overlapping signaling pathways to regulate microglial activation and Aβ clearance. Here, we review the current understanding of CD33 and TREM2 biology in AD, with a focus on their potential crosstalk and functional antagonism. We propose potential mechanistic models by which human CD33 isoforms regulate TREM2 activity in either the absence or presence of Aβ pathology and discuss therapeutic strategies targeting this axis. Together, these insights suggest new avenues for microglia-targeted interventions in AD.