Impact of subclinical pp65 antigenemia (≥ 1cell/slide) during the first 80 days on recovery of CMV-specific CD4⁺ Th responses and CD8⁺ CTL responses at 3 months among patients receiving prophylactic ganciclovir at engraftment. PHA indicates phytohemagglutinin and represents a nonspecific antigen recognized by CD4⁺ cells.