Carboxyfluorescein diacetate succinimidyl ester and the virgin lymphocyte:A marriage made in heaven

Carboxyfluorescein diacetate succinimidyl cater (CFSE) labelling of naive l ymphocyte populations provides unique insights into the immune response. Th e clonal nature of immune responses, necessitating clonal expansion to achi eve a sufficiently large number of Ag-reactive effector cells, combined wit h the dependence of lymphocyte differentiation on cell division, underlie t he usefulness of CFSE in understanding the factors that regulate responses both in vitro and in vivo. Pie have combined CFSE labelling with Ag recepto r transgenic models, using seven channel flow cytometry to track the correl ation between cell division and a number of other parameters, such as surfa ce expression of activation markers, cytokine receptors and homing receptor s, cytokine production, cytotoxic activity and indicators of apoptosis. Our data have allowed us to classify and understand immune responses in novel ways, suggesting many further avenues of enquiry and indicating previously unrecognized relationships between cell division and eventual cell face.