What is Positive selection regarding T-cells?

Low affinity interaction between abTCR and MHC molecules sends survival signal. These cells may recognize complexes of microbial antigens bond to MHC with higher affinity. Cell that cannot recognize MHC molecules will die. Cells that recognize class I MHC will retain CD8, and cells that recognize class II MHC will retain CD4. this will generate single-positive T cells.