Macropinocytosis is a form of endocytosis that accompanies cell surface 
ruffling. It is distinct in many ways from the better characterized 
micropinocytosis, which includes clathrin-coated vesicle endocytosis and small 
uncoated vesicles. Because macropinosomes are relatively large, they provide an 
efficient route for non-selective endocytosis of solute macromolecules. This 
route may facilitate MHC-class-II-restricted antigen presentation by dendritic 
cells. Because the ruffling that leads to macropinocytosis is regulated, it has 
been exploited by some pathogenic bacteria as a novel route for entry into 
cells.