Microbiology Practice Exam

What primarily triggers the action of eosinophils during an immune response?

1. Bacterial infections

2. Allergic reactions

3. Parasitic invasions

4. Viral infections

The correct answer is: Parasitic invasions

Eosinophils are a type of white blood cell that play a crucial role in the immune response, particularly in combating parasitic infections. Their activation is primarily triggered by the presence of larger parasites, such as helminths (worms), which are too large for phagocytosis by other immune cells. The eosinophils recognize and bind to these parasites through specific receptors that detect immunoglobulin E (IgE) or complement proteins that have coated the parasites. Once activated, eosinophils release various cytotoxic granules and inflammatory mediators, such as eosinophilic cationic protein and major basic protein, which help to damage the surface of the parasites and can lead to their destruction. This targeted response is essential for the effective elimination of parasitic threats. While eosinophils can also be involved in allergic reactions, their primary role and the trigger of their most significant activity relate to parasitic invasions. Thus, understanding the specific functions and triggers of eosinophils highlights their importance in parasitic defense, which differentiates them from roles played by immune cells in responses to bacteria and viruses.