Cutting edge: polarized Th cell response induction by transferred antigen-pulsed dendritic cells is dependent on IL-4 or IL-12 production by recipient cells.

To assess the influence of dendritic cell (DC) production of polarizing cytokines on Th2 and Th1 development we transferred Ag-pulsed DC generated from wild-type, IL-4(-/-), or IL-12(-/-) mice into wild-type, IL-4(-/-), or IL-12(-/-) recipients. We found that DC IL-4 was not necessary for Th2 induction and that, surprisingly, DC IL-12 was not an absolute requirement for Th1 development. However, DC IL-12 production facilitated optimal Th1 response development. Critically, recipient ability to produce IL-4 or IL-12 was essential for either Th2 or Th1 development. These data help delineate the source and importance of IL-4 and IL-12 in the process of induction of polarized T cell responses by DC.