MHC molecules and microbial antigen processing in phagosomes.

Macrophages and dendritic cells are phagocytic antigen presenting cells that internalize bacteria and other particulate antigens into phagosomes. The phagosome must then balance microbicidal and proteolytic degradation functions with the generation of antigenic peptides for presentation by class I and class II MHC molecules to CD8 and CD4 T cells, respectively. Understanding the host and bacterial factors that affect phagosomal antigen processing may help facilitate new strategies to eliminate pathogens.