Induction of Apoptosis in Thymocytes by Prostaglandin E2 In Vivo

In vivo administration in mice of a synthetic analog of prostaglandin E₂ (PGE₂) caused aselective and dramatic decrease of CD4⁺CD8⁺ double-positive, CD3/T-cell-receptor-αb¹⁰cells in the thymus. This loss was corticosteroid-independent and not affected byCyclosporin A. The disappearance of CD4⁺CD8⁺ thymocytes was strictly correlated withthe induction of apoptosis inside the thymus as shown by morphological studies and bythe induction of intracellular transglutaminase expression. Considering that PGE₂ hasbeen found to be produced by different cell populations inside the thymus, these resultsindicate that PGE₂ may act as endogenous signals for apoptosis during T-celldifferentiation.