CD11a, also known as Lymphocyte Function-Associated Antigen 1 (LFA-1) alpha chain or integrin alpha L, is an adhesion molecule primarily expressed on leukocytes such as Leu[A5] cells. It plays a crucial role in cellular adhesion by binding to intercellular adhesion molecules (ICAMs) like ICAM-1 (CD54), ICAM-2 (CD102), and ICAM-3 (CD105). Additionally, CD11a can interact with JAM-1, facilitating the passage of leukocytes across endothelial cells. CD11a has various functions in the immune system. For instance, in primary immune thrombocytopenia (ITP), CD11a is expressed on regulatory T cells (Tregs) and interacts with antigen-presenting cells (APCs) to participate in immune regulation. Furthermore, CD11a is associated with the progression of rheumatoid arthritis (RA) and is considered an important factor in the pathogenesis of the disease. In cancer therapy, CD11a also shows promising potential. Researchers have found that activating molecules like CD11a on the surface of macrophages can enhance their ability to kill cancer cells, providing a hopeful approach for cancer treatment.