ICAM5 (intercellular adhesion molecule 5) functions as a cell adhesion molecule with dual roles in neuronal development and pathological processes. In the nervous system, ICAM5 promotes homophilic cell-cell adhesion that enhances dendritogenesis and arborization of hippocampal neurons, supporting normal neuronal development and connectivity 1. The protein serves as a receptor ligand for integrin ITGAL:ITGB2/LFA-1, facilitating neuron-leukocyte adhesion interactions 1. ICAM5 expression is regulated by DNA methyltransferases DNMT1 and DNMT3a, which induce promoter hypermethylation leading to transcriptional activation 1. In disease contexts, ICAM5 demonstrates complex associations with various pathological conditions. Mendelian randomization studies identify ICAM5 as a potential therapeutic target, with protective effects against intracranial aneurysms 2 and lung adenocarcinoma 34, while also being implicated in critical COVID-19 pathogenesis through myeloid cell adhesion mechanisms 5. However, in thyroid carcinoma, ICAM5 overexpression promotes tumor progression through activation of MAPK/ERK and MAPK/JNK signaling pathways, enhancing cell proliferation, mobility, and tumorigenic activity 1. Additionally, ICAM5 variants show associations with systemic lupus erythematosus susceptibility 6 and interactions with air pollution in depression risk 7.