Activated T Lymphocytes Disappear from Circulation during Endotoxemia in Humans

Seventeen volunteers received an intravenous bolus of endotoxin (2 ng/kg of body weight). Endotoxin-induced lymphopenia was constituted mainly by cells with an immature phenotype (CD45RA(+) CD45RO(−)) that were less likely to undergo apoptosis (CD28(+)), whereas cells with the highest rates of disappearance were characterized by an activated phenotype (CD45RA(−) CD45RO(+)) as well as a phenotype linked to apoptosis (CD95(+) CD28(−)). In conclusion, endotoxin-induced lymphopenia reflects the disappearance from the circulation of activated lymphocytes prone to undergo apoptosis.