Proliferation kinetics of Sezary cells

The proliferation kinetics of neoplastic T cells arising in Sezary syndrome (Sezary cells) are still poorly understood. Kinetic studies with ³H-thymidine as a DNA precursor revealed a low incorporation rate of the nucleotide into Sezary cells obtained from the peripheral blood versus Sezary cells from the skin. Using the double-label autoradiography we determined the duration of single cell cycle phases of blood and cutaneous Sezary cells. The results indicate the almost complete lack of proliferative activity in the blood but a considerable portion of proliferatively active Sezary cells in skin infiltrates. The removal of a large mass of quiescent blood cells by leukapheresis did not affect the proliferative state of the residual peripheral cell population implying that the procedure did not induce the migration of proliferating skin cells towards the blood. Terminally, the disease underwent transition into immunoblastic lymphoma. At this time, the kinetic behavior of the peripheral immunoblasts showed great similarity to that of cutaneous Sezary cells. The findings point towards a common extravascular production site of Sezary cells and immunoblasts probably located in the lymphatic tissue.