Proliferation kinetics of Sézary cells

The proliferation kinetics of neoplastic T cells arising in Sézary syndrome (Sézary cells) are still poorly understood. Kinetic studies with 3H-thymidine as a DNA precursor revealed a low incorporation rate of the nucleotide into Sézary cells obtained from the peripheral blood versus Sézary cells from the skin. Using the double-label autoradiography we determined the duration of single cell cycle phases of blood and cutaneous Sézary cells. The results indicate the almost complete lack of proliferative activity in the blood but a considerable portion of proliferatively active Sézary 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 Sézary cells. The findings point towards a common extravascular production site of Sézary cells and immunoblasts probably located in the lymphatic tissue.