Kinetics of dendritic cell activation: impact on priming of TH1, TH2 and nonpolarized T cells

Abstract

To prime immune responses, dendritic cells (DCs) need to be activated to acquire T cell stimulatory capacity. Although some stimuli trigger interleukin 12 (IL-12) production that leads to T helper cell type 1 (T_H1) polarization, others fail to do so and favor T_H2 polarization. We show that after activation by lipopolysaccharide, DCs produced IL-12 only transiently and became refractory to further stimulation. The exhaustion of cytokine production impacted the T cell polarizing process. Soon after stimulation DCs primed strong T_H1 responses, whereas at later time points the same cells preferentially primed T_H2 and nonpolarized T cells. These findings indicate that during an immune response, T cell priming conditions may change in the lymph nodes, suggesting another mechanism for the regulation of effector and memory T cells.