To purify human naïve and memory CD4 T cells from PBMC, fresh PBMC were stained with antibodies specific for cell surface markers and CD4+CD8-CD14-CD123-CD45RA+CD45RO-(naïve CD4 T cells) and CD4+CD8-CD14-CD123-CD45RA-CD45RO+ (memory CD4 T cells) were sorted on a FACSAria (BD Bioscience, San Jose, CA).