Activated T Lymphocytes Disappear from Circulation during Endotoxemia in Humans

Abstract
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.