Name a common adverse effect of interferon therapy.

Flu-like symptoms are indeed a common adverse effect associated with interferon therapy. Interferons, which are cytokines used in the treatment of various viral infections and some cancers, can elicit responses in the body that mimic the symptoms of a viral infection. These include fever, chills, fatigue, muscle aches, and malaise, all of which are characteristic of flu-like symptoms. This reaction is generally due to the immune-modulating effects of interferons, as they stimulate the immune system, potentially leading to these systemic signs of an activated immune response.

While nausea can occur with various medications, it is not as specific or common as flu-like symptoms when it comes to interferons. Insomnia can also be a side effect but is less prevalent compared to the flu-like symptoms. Weight gain is not typically associated with interferons; rather, these medications can sometimes lead to weight loss due to their effects on metabolism and appetite. Therefore, flu-like symptoms are the hallmark adverse effect, making this answer particularly relevant in the context of interferon therapy.