Background The cytokines IL-4 and IL-10 have been implicated in the regulation of T cell proliferation and differentiation. IL-4 drives the development of Th2 cells from naive precursors and it is supposed to enhance T cell proliferation, whereas IL-10 has been suggested to support the differentiation of regulatory Th cells and to negatively affect T cell proliferation.
Objectives To analyse the proliferation and stability of cytokine expression of individual cytokine-producing T cells.
Methods We established the cellular affinity matrix technology for the immunofluorescent identification and isolation of IL-4- or IL-10-secreting cells. With this technology we purified IL-4- or IL-10-secreting and non-secreting Th cells, labelled them with the fluorescent dye CFSE to track their proliferation after antigen-specific or polyclonal restimulation, and analysed their cytokine expression upon later restimulation.
Results Previously, we have shown that naive Th cells have to enter the initial S phase of the first cell cycle to respond to an IL-4 signal by production of IL-4 or IL-10 upon restimulation. By direct counterstaining of cytokines and DNA content we now tested whether in general cytokine production is restricted to certain cell cycle phases, which we found not to be the case. The isolated IL-4+ and IL-4- T cells showed the same proliferation behaviour over 6 days, and the sorted IL-10+ cells were not inhibited in their proliferation compared with the IL-10- T cells. Thus, neither IL-4 nor IL-10 production by an individual T cell directly influences the proliferation of the same cell. When we analysed the stability of cytokine memory of the sorted T cells in later restimulations, a substantial fraction of the purified cytokine-producing cells did not reexpress the cytokine that it had expressed in an earlier stimulation.
Conclusion Thus, there is a certain degree of instability in the cytokine memory of Th cells, the molecular basis of which we are currently analysing.
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