Final answer:
Antibodies cannot destroy viruses within cells, but cytotoxic T cells and NK cells are essential in fighting intracellular infections by recognizing and destroying infected cells. HIV evades immune responses by targeting CD4-positive cells and integrating into the host genome, challenging treatment efforts.
Step-by-step explanation:
Antibodies are unable to destroy viral invaders that enter a normal cell and multiply within the cell. Viruses exploit specific binding sites on cell surfaces to invade cells, and once inside, they replicate using the cell's machinery. Although the immune system can produce antibodies in response to proteins on the virus's surface, antibodies themselves cannot penetrate the plasma membrane to affect intracellular pathogens.
Interferons may slow viral replication, but they have limited ability to eradicate viruses. Instead, cytotoxic T cells and NK cells play a critical role in fighting intracellular viral infections. Cytotoxic T cells can identify and destroy infected cells by recognizing altered class I MHC molecules, which are downregulated by many virally infected cells.
Viruses like HIV present additional challenges. HIV targets CD4-positive white blood cells and integrates into the host cell's genome, making it harder to treat. Unlike antibodies, cytotoxic T cells and NK cells possess mechanisms to tackle infected cells, emphasizing their importance in viral containment and immune system defense.