Final answer:
Dendritic cells can present antigens from various types of pathogens, including intracellular bacteria, extracellular pathogens, and cancer cells, through the process of cross-presentation.
Step-by-step explanation:
Dendritic cells, key components of the immune system, have the unique capability of presenting antigens from various types of pathogens, including intracellular bacteria, viruses, and cancer cells. One particular method, known as cross-presentation, enables dendritic cells to capture extracellular antigens and present them on both MHC class I and class II molecules.
In the context of an extracellular bacterial infection, dendritic cells engage in receptor-mediated endocytosis to internalize the bacteria. Once inside, lysosomes digest the bacteria, and the dendritic cells then present the antigenic fragments using MHC class II molecules. Cross-presentation also allows these antigens to be presented on MHC class I molecules, thus eliciting a CD8 T cell response, even though these cells typically recognize intracellular pathogens. This mechanism ensures a robust and flexible immune response capable of targeting a wide range of pathogens, including those that do not directly infect the cytoplasm of cells.