CD4 and influenza: Similar to previously discussed studies in acute influenza infection, Stary and others (2009) demonstrated in HIV infection that pDC-derived IFN-α led to expression of TRAIL on pDCs and CD4+ T cells and concomitant death receptors (TRAIL-R2) on CD4+ T cells; this interaction induced apoptosis of uninfected CD4+ T cells and consequently severe host pathology.