What is the correct order of events occurring in the body after exposure to an allergen?

The sequence in choice B accurately represents the process that occurs after exposure to an allergen. Initially, when the body encounters an allergen, the immune system recognizes it as a threat. This recognition leads to the activation of white blood cells (WBC), specifically B cells or T cells, depending on the type of allergic response.

Once these WBCs are activated, they begin to produce specific antibodies, such as immunoglobulin E (IgE), which bind to the allergen. This binding triggers a cascade of biochemical responses, including the production and release of leukotrienes. Leukotrienes are inflammatory mediators that contribute to various allergic symptoms by causing bronchoconstriction, increased vascular permeability, and attracting additional immune cells to the site of exposure.

Finally, the reaction by the body encompasses the physical symptoms and responses associated with the allergy, such as sneezing, itching, or difficulty breathing. This sequence highlights the coordinated response of the immune system to allergens and emphasizes how the activation of WBC leads to leukotriene production, which then results in the body's overall reaction to the allergen. Such understanding is crucial in comprehending the pathophysiology of allergic reactions and the subsequent treatment strategies.