CD99 antigen-like protein 2

CD99L2 (CD99 antigen-like protein 2) is a 262-amino acid homophilic adhesion molecule involved in leukocyte extravasation, particularly in helping immune cells traverse the endothelial basement membrane independently of PECAM1 (UniProt: Q8TCZ2). Its precise molecular interactions and trafficking mechanisms remain incompletely characterized, though it shares functional similarities with CD99.

The protein is expressed in tissues involved in immune cell trafficking and vascular biology. UniProt records no curated disease associations for CD99L2 at the sequence level (UniProt: Q8TCZ2).

CD99L2 is implicated in Alzheimer's Disease pathology. Chaparral AD proteomics analysis of human post-mortem brain tissue from AD patients versus age-matched controls detected CD99L2 as significantly upregulated (mean log2FC = 0.4772) in a single subcellular fraction across TMT-labeled DDA proteomics (Chaparral AD proteomics). The upregulation pattern suggests a potential role in neuroinflammatory or vascular responses associated with AD neurodegeneration, though the functional significance remains to be elucidated.