CD99 antigen

CD99 antigen is a 185-amino acid cell surface glycoprotein involved in T-cell adhesion and leukocyte extravasation. It facilitates T-cell adhesion processes and mediates spontaneous rosette formation with erythrocytes, playing a role in helping leukocytes cross the endothelial basement membrane independently of PECAM1 (UniProt: P14209).

The protein is primarily involved in immune cell trafficking and adhesion processes. UniProt records no inherent disease associations for CD99, though it has been linked historically to leukemias and lymphomas through other databases.

CD99 shows disease relevance to Alzheimer's Disease based on curated AD proteomics data. The protein is significantly upregulated in post-mortem AD brain tissue compared to age-matched controls (mean log2 fold-change: 0.5811, Chaparral AD proteomics). This upregulation was detected across one subcellular fraction in a TMT-labeled quantitative proteomics study of four subcellular compartments (P2, P3, S2, S3). The biological significance of elevated CD99 in AD brain warrants further investigation into potential immune or vascular contributions to neurodegeneration.