The effector cells of the immune system are able to recognize the infected cells , transformed , and how recently found , cells of various types of stressors . One way is to recognize the identification of the latter, stress-induced cell surface molecules . The best known receptor involved in this type of reaction is the C -type lectin receptor called NKG2D on NK cells present , TGD lymphocytes , CD8 + lymphocytes and macrophages Tab . Described 4 NKG2D ligand family . These are human molecules MIC A and B ( sometimes also referred to as MICA and MICB ) and ULBP and the mouse RAE -1 and H60 .