Final answer:
Opportunistic pathogens infect immune system cells and allow for the development of opportunistic infections when host defenses are compromised.
Step-by-step explanation:
Pathogens that infect cells of the immune system and allow opportunistic infections to develop are known as opportunistic pathogens.
These pathogens can only cause disease when the immune system is compromised, such as in individuals with weakened immune systems or conditions that compromise immune defenses.
Opportunistic pathogens take advantage of situations that compromise the host's defenses, such as the body's protective barriers, immune system, or normal microbiota.