Which white blood cell type includes T cells and B cells and is central to adaptive immunity?

Which white blood cell type includes T cells and B cells and is central to adaptive immunity?

• A. Eosinophil
• B. Megakaryocyte
• C. Monocyte
• D. Lymphocytes

Answer: (D)

Lymphocytes are the white blood cells that include T cells and B cells and are central to adaptive immunity. They recognize specific antigens, generate targeted responses, and form memory so the body can respond faster in later encounters. T cells coordinate immune responses and can kill infected cells or help other immune cells, while B cells produce antibodies that neutralize pathogens. The other options don’t fit this role: eosinophils are primarily involved in defense against parasites and allergic reactions; megakaryocytes are large bone marrow cells that give rise to platelets; monocytes are part of the innate immune system and differentiate into macrophages or dendritic cells for phagocytosis and general antigen presentation, not the specific antigen-targeted functions of adaptive immunity.

Lymphocytes are the white blood cells that include T cells and B cells and are central to adaptive immunity. They recognize specific antigens, generate targeted responses, and form memory so the body can respond faster in later encounters. T cells coordinate immune responses and can kill infected cells or help other immune cells, while B cells produce antibodies that neutralize pathogens. The other options don’t fit this role: eosinophils are primarily involved in defense against parasites and allergic reactions; megakaryocytes are large bone marrow cells that give rise to platelets; monocytes are part of the innate immune system and differentiate into macrophages or dendritic cells for phagocytosis and general antigen presentation, not the specific antigen-targeted functions of adaptive immunity.