Final answer:
To escape host defenses, pathogens may develop protective structures, like complex cell walls, avoid immune detection through antigenic variation or produce substances that impair immune cells, such as toxins hindering phagocytosis or viruses depleting critical immune cells.
Step-by-step explanation:
Pathogens can escape host defenses by utilizing several mechanisms. One common strategy is to develop a complex cell wall that is resistant to the digestive enzymes of phagocytes, like in the case of Mycobacterium tuberculosis, which causes the chronic disease tuberculosis. Others produce protective capsules to avoid phagocytosis or alter their surface antigens to evade immune detection, a process known as antigenic variation. Besides, pathogens like Staphylococcus aureus produce toxins that kill phagocytes, and viruses like HIV can infect and deplete T cells critical for adaptive immunity.
These stealth methods allow pathogens to not only persist in the host but also spread by hiding within or directly countering the immune system's mechanisms. The evolutionary arms race between host immune defenses and pathogens results in pathogens often having ways to outwit immune responses, ensuring their survival and continuation.