Drinking a lot is good for dendritic cells

Abstract

Macropinocytosis is the actin-dependent formation of large vesicles, which allow the internalization of large quantities of fluid-phase solute. In the majority of cells examined, an exogenous stimulus is required to induce the initiation of this endocytic pathway. However, dendritic cells are thought to constitutively macropinocytose large quantities of exogenous solute as part of their sentinel function. In this review we discuss the evidence that dendritic cells macropinocytose exogenous solute and subsequently present antigenic peptides derived from internalized material to T cells. In addition, we put these data into the context of immune surveillance in vivo.

Figure 1

Time-lapse video-microscopy of macropinosome formation in murine bone-marrow-derived DC. The formation and fate of two macropinosomes formed at the leading edge of a DC cultured in the absence of growth factors for 24 hr prior to examination. At 0 seconds a macropinsome forms (black arrow) and subsequently (40–280 seconds) traffics towards the nucleus. At 40 seconds a large circular ruffle forms at the leading edge of the DC (white arrow), closes off to form a macropinosome (100 seconds), fuses with other large vesicles (180 seconds) and finally fuses with the initial macropinosome.

Figure 3

Schematic of macropinocytosis in DC.

Figure 2

Release of exogenous solute into the cytosol of a murine bone-marrow-derived DC. DC were cultured at 37°C in the presence of 1 mg/ml fluorescein isothiocyanate (FITC)-dextran (40 000 MW), then washed and chased in the presence of Trypan Blue that will quench FITC fluorescence if it is accessible from outside the cell. FITC fluorescence is not quenched, and so is in an intact living cell.