CD4 and infection: CD38+ CD4+ T cells stained negatively for the apoptotic marker Annexin-V and the viability stain propidium iodide (Pi) prior to infection (98.4±0.5% Annexin-V-, 99.8±0.5% Pi-) and during infection (98.8±0.8% Annexin-V-, 99.8±0.2% Pi-).