Which of the following types of white blood cells exists as two types-- the B cell and T cell?

Lymphocytes are a crucial component of the immune system and are classified into two main types: B cells and T cells. B cells are responsible for producing antibodies that help identify and neutralize foreign objects like bacteria and viruses. In contrast, T cells play key roles in cell-mediated immunity, recognizing and destroying infected cells or coordinating the immune response. The versatility of lymphocytes is fundamental to the adaptive immune response, which provides long-lasting protection against specific pathogens.

Other white blood cells, such as neutrophils, basophils, and monocytes, each have distinct roles but do not exist as two different types in the same way lymphocytes do. Neutrophils primarily act in the innate immune response, attacking bacteria through phagocytosis. Basophils are involved in allergic reactions and inflammation by releasing histamine. Monocytes differentiate into macrophages and dendritic cells, which also play roles in the immune defense but do not further differentiate into subtypes like B and T cells. Thus, the classification of lymphocytes as encompassing both B and T cells highlights their unique and adaptable functions within the immune system.