Which statement best describes a primary function of B cells?

Which statement best describes a primary function of B cells?

• A. They engulf and digest pathogens with phagocytosis
• B. They regularly present antigen with MHC I to cytotoxic T cells
• C. They differentiate into platelets to promote coagulation
• D. They produce antibodies and develop memory responses

Answer: (D)

B cells are central to humoral immunity because their main job is to make antibodies and create memory. When a B cell encounters its specific antigen and receives help from a helper T cell, it becomes activated, proliferates, and differentiates into plasma cells that secrete antibodies. These antibodies neutralize pathogens and mark them for destruction. A portion of the activated cells becomes memory B cells, which persist long-term and respond more rapidly upon re-exposure. B cells primarily present antigen to helper T cells via MHC class II, not to cytotoxic T cells via MHC class I, which helps clarify why they aren’t described as presenting to cytotoxic T cells. Phagocytosis is carried out by macrophages and neutrophils, and platelets arise from megakaryocytes, not B cells. So the best description of their primary function is producing antibodies and developing memory responses.

B cells are central to humoral immunity because their main job is to make antibodies and create memory. When a B cell encounters its specific antigen and receives help from a helper T cell, it becomes activated, proliferates, and differentiates into plasma cells that secrete antibodies. These antibodies neutralize pathogens and mark them for destruction. A portion of the activated cells becomes memory B cells, which persist long-term and respond more rapidly upon re-exposure. B cells primarily present antigen to helper T cells via MHC class II, not to cytotoxic T cells via MHC class I, which helps clarify why they aren’t described as presenting to cytotoxic T cells. Phagocytosis is carried out by macrophages and neutrophils, and platelets arise from megakaryocytes, not B cells. So the best description of their primary function is producing antibodies and developing memory responses.