CD4+CD7- leukemic T cells from patients with Sezary syndrome are protected from galectin-1-triggered T cell death

In early stages of cutaneous T cell lymphoma (Sezary syndrome) both CD4(-)CD7(-) and CD4(+)CD7(+) T cells clonally expand whereas In late stages of the disease CD7(-) cells are predominant In number, giving rise to the question whether CD7(-) T cells have a survival advantage In the skin. Galectin-1, a cell-bound lectin, was recently reported to trigger apoptosis in activated CD7(+) T cells. Here, we demonstrate that in contrast to activated CD7(+) T cells, quiescent and activated CD69(+) CD7(-) T cells from healthy donors and from Sezary patients are resistant to galectin-1-mediated cell death. CD7(-) T cells are apoptosis-resistant even during coculture with IFN-gamma-stimulated endothelial cells that constitutively express galectin-1 in high amounts. These data Imply that resistance of CD7(-) T cells to galectin-1-induced apoptosis may contribute to the accumulation of CD7(-) Sezary T cells during progression of the disease.