Final answer:
Dendritic cells can present a variety of pathogens including intracellular viruses, extracellular toxins, allergens, and protozoa. Intracellular viruses are presented on class I MHC molecules to cytotoxic T cells, and extracellular pathogens are presented on class II MHC molecules to helper T cells.
Step-by-step explanation:
Dendritic cells are a type of antigen-presenting cell that can present a variety of pathogens, ranging from intracellular viruses to extracellular toxins , allergens, and even protozoa. These pathogens are processed differently depending on whether they are intracellular or extracellular.
Intracellular viruses are presented on class I MHC molecules to cytotoxic T cells, which is crucial because viruses infect cells and replicate within them. These infected cells can be found throughout the body, necessitating that all body tissues express class I MHC to elicit a T cell response. On the other hand, extracellular pathogens like bacteria, parasites, and fungi, as well as allergens and toxins that do not replicate within the cell's cytoplasm, are usually presented on class II MHC molecules to helper T cells.
The type of pathogen presented by dendritic cells is extracellular antigens. Dendritic cells are antigen-presenting cells that phagocytize pathogens and place them into vesicles. Extracellular antigens, such as those from bacteria, parasites, and fungi, are brought into the endomembrane system of the cell and presented on MHC class II molecules on the cell surface.