Macroautophagy has recently emerged as an important catabolic process involved not only in innate immunity but also in adaptive immunity. Initially described to deliver intracellular antigens to MHC class II loading compartments, its molecular machinery has now also been described to enhance the delivery of extracellular antigens to MHC class II loading compartments by accelerating phagosome maturation. Therefore in pathological situations (viral or bacterial infections, tumorigenesis) the pathway might be involved in shaping CD4+ T cell responses.
In this chapter we describe three basic experiments for the monitoring and manipulation of macroautophagic antigen processing towards MHC class II presentation. Firstly, we will discuss how to monitor autophagic flux and autophagosome fusion with MHC class II loading compartments. Secondly, we will show how to target proteins to autophagosomes in order to monitor macroautophagy-dependent antigen processing via their enhanced presentation on MHC class II molecules to CD4+ T cells. And finally, we will describe how macroautophagy can be silenced in antigen presenting cells, like human monocyte-derived dendritic cells (DCs).