28 years old man was presented to having fever and fatigue. He had difficulty breathing, headache and very unwell. However, all bacteriology related...

28 years old man was presented to having fever and fatigue. He had difficulty breathing, headache and very unwell. However, all bacteriology related work indicated no causative agent. The patient Igs levels were tested and there was a slightly elevated IgE level in addition to high levels of IgG. The patient showed no allergies to any of the agents in the allergy test.

What other test you would do to determine the cause of the illness? Why would you take such a step?

Why IgE levels are important in this case? Why IgE is referred to as the only harmful antibody?

What does fever mean in general and why is it not looked at as a specific symptom?

How could levels of Immunoglobulins assist in determine the type of antigen a person is infected with? Give examples of how levels of Igs can assist to determine the causative agent.