Generation of antigen-specific Th2 cells from unprimed mice in vitro: effects of dexamethasone and anti-IL-10 antibody.

We describe a system for the in vitro production of Ag-specific mouse CD4 cell lines from unprimed mice. Purified CD4+ CD45RB(high) T cells were exposed to Ag-pulsed accessory cells in serum-free medium for 24 h; cultured in the absence of Ag and in the presence of serum, IL-2, dexamethasone, and Abs to IL-10 for an additional 4 days; and then re-exposed to the original sensitizing Ag. The presence of dexamethasone and Abs to IL-10 during the initial expansion stage appeared to be critical for the ability of the stimulated and expanded T cells to respond to restimulation with the same Ag. Repeated cycles of in vitro stimulation led to increased specificity for the sensitizing Ag (in the current case, pigeon cytochrome c), a decline in production of IL-2 and IFN-gamma, and increased production of IL-4, IL-5, and IL-10. This culture protocol provides a test system for exploration of factors that regulate the conversion of naive cells to memory cells and the development of specific immune responses to protein Ags. The data are consistent with models that implicate glucocorticoids as regulators of immune response specificity.