ICAM1 is a 85-110 kDa single chain type 1 integral membrane glycoprotein with an extracellular domain of five immunoglobulin superfamily repeats, a transmembrane region and a cytoplasmic domain. It shares considerable amino acid sequence homology with ICAM3 and with ICAM2. ICAM1 is expressed by activated endothelial cells. It is detected on cells of many other lineages (e.g. epithelial cells, fibroblasts, chondrocytes, B lymphocytes, T lymphocytes (low), monocytes, macrophages, dendritic cells and neutrophils), with lower levels that increase in inflammation. ICAM1 is also detected in some carcinoma and melanoma cells. Soluble ICAM1 is detectable in the plasma and is elevated in patients with various inflammatory syndromes. It is the receptor for rhinoviruses and malaria.