Here's why:

* Specificity: Interferons are primarily effective against viruses. They trigger a cascade of responses within the infected cell, ultimately inhibiting viral replication.

* Limited Action: While some interferons have shown limited activity against certain bacteria and parasites, their primary role remains in antiviral defense.

* Pathogen Variation: The effectiveness of interferons can vary depending on the specific virus involved. Some viruses have developed mechanisms to evade interferon responses.

Therefore, interferons are not a universal solution for all pathogens. They are a crucial component of the immune response against viral infections, but their effectiveness against other pathogens is limited.