Final answer:
Extracellular pathogens have access to components of the immune system involved in the humoral response, such as antibodies. The innate immune system, including macrophages and dendritic cells, plays a crucial role in identifying and engulfing extracellular pathogens.
Step-by-step explanation:
Extracellular pathogens have access to components of the immune system that are involved in the humoral response. The humoral response is part of the acquired immune system and is responsible for producing protective molecules called antibodies. These antibodies are able to recognize and bind to antigens on the surface of extracellular pathogens, marking them for destruction by other immune cells.
When a pathogen enters the body, cells in the blood and lymph detect specific pathogen-associated molecular patterns (PAMPs) on the pathogen's surface. The innate immune system has specific cells, such as macrophages and dendritic cells, with receptors called pattern recognition receptors (PRRs) that recognize these PAMPs. These cells play a crucial role in identifying and engulfing extracellular pathogens.
Furthermore, extracellular antigens from bacteria are brought into the endomembrane system of host cells through receptor-mediated endocytosis. The resulting vesicle fuses with vesicles from the Golgi complex, which contain pre-formed MHC class II molecules. After fusion of these vesicles and the association of antigen and MHC, the new vesicle makes its way to the cell surface for presentation to immune cells, triggering an immune response against the extracellular bacterial infection.