sentences:  Upregulation of Mac-1 in the presence of certain factors such as IL-2 may cause a prolongation of the life of the immune cell while the presence of TNF-α induces apoptosis and selective removal of the cell.A fully activated neutrophil may express on its membrane 200,000 or more CR3 molecules.Absence of CR3 results in reduced binding and ingestion of "Mycobacterium tuberculosis" in mice.