Activated human epitope-specific T cells identified by class II tetramers reside within a CD4high, proliferating subset
Antigen-specific T cells acquire a distinctive phenotype during activation, with characteristic acquisition of surface markers and patterns of gene expression. Early after antigen stimulation, CD4+ T lymphocytes increase their surface density of the CD4 marker, a trait which has been used to identify antigen-activated cells. The recent development of MHC tetramer technologies has greatly improved