Infiltration of tumours by macrophages and dendritic cells: tumour-associated macrophages as a paradigm for polarized M2 mononuclear phagocytes.

Macrophages and dendritic cells infiltrate tumours. In the tumour microenvironment, mononuclear phagocytes acquire properties of polarized M2 (or alternatively activated) macrophages. These functionally polarized cells, and similarly oriented or immature dendritic cells present in tumours, play a key role in subversion of adaptive immunity and in inflammatory circuits which promote tumour growth and progression.