ICAM-1 expression increased on PMN from patients with TAO, which suggested that PMN from these patients not only exhibited enhanced reactive oxygen species generation, improved phagocytosis, and elevated levels of endotoxin, but also bound to the lymphocyte function associated antigen-1 of T cells to affect T-cell activation (18–21). This evidence concerns the gene ICAM1 and thromboangiitis obliterans.