Canadian Society for Medical Laboratory Science (CSMLS) Practice Exam

Which type of white blood cell is primarily involved in allergic reactions?

1. Neutrophils

2. B lymphocytes

3. Eosinophils

4. T lymphocytes

The correct answer is: Eosinophils

Eosinophils are the type of white blood cells primarily involved in allergic reactions. They play a crucial role in the immune response to allergens and parasitic infections. Eosinophils are particularly effective in combating larger parasites that cannot be engulfed by phagocytes, and they release various substances, such as cytokines and inflammatory mediators, that contribute to the development and exacerbation of allergic reactions. During an allergic response, eosinophils are attracted to the site of inflammation by signals from other immune cells and participate in the inflammatory process by releasing granules that contain enzymes and other agents that can damage tissues and induce inflammation. Their presence is often associated with conditions such as asthma, hay fever, and other allergic diseases. In contrast, neutrophils are primarily involved in the early response to infections and are key players in the body's defense against bacterial infections. B lymphocytes are responsible for antibody production; while they can be involved in certain aspects of the allergic response, their main function is not directly tied to the mediation of allergic reactions. T lymphocytes, particularly T-helper cells, can modulate immune responses and contribute to allergy development indirectly, but they do not directly mediate the allergic reaction itself like eosinophils do.