Quantitative analysis of lymphocyte differentiation and proliferation in vitro using carboxyfluorescein diacetate succinimidyl ester

Mature T and B lymphocytes respond to receptor-delivered signals received d uring and following activation. These signals regulate the rates of cell de ath, growth, differentiation and migration that ultimately establish the be haviour patterns collectively referred to as immune regulation. We have bee n pursuing the philosophy that in vitro systems of lymphocyte stimulation, when analysed quantitatively, help reveal the logical attributes of lymphoc yte behaviour. The development of carboxyfluorescein diacetate succinimidyl ester (CFSE) to track division has enabled the variable of division number to be incorporated into these quantitative analyses. Our studies with CFSE have established a fundamental link between differentiation and division n umber. Isotype switching, expression of T cell cytokines, surface receptor alterations and changes to intracellular signalling components all display independent patterns of change with division number. The stochastic aspects of these changes and the ability of external signals to independently regu late them argue for a probabilistic modelling framework for describing and understanding immune regulation.