Which type of white blood cell is least common and associated with allergic responses?

Basophils are the least common type of white blood cell, making up only a small percentage of the total white blood cell count. They play a crucial role in the body's response to allergens and are involved in inflammatory reactions. Basophils release histamine and other mediators that contribute to the symptoms associated with allergic reactions, such as itching, swelling, and vasodilation. Their presence and activity are crucial in the pathophysiology of allergies and asthma, making it essential to recognize their significance in the context of immune responses.

In contrast, lymphocytes are primarily involved in the adaptive immune response, monocytes are key players in the innate immune response and act as phagocytes, while neutrophils are the most abundant type of white blood cells and are primarily responsible for combating bacterial infections. Thus, while all these white blood cells contribute to immune function, basophils are specifically noted for their association with allergic responses and are characterized by their rarity within the white blood cell population.