Chapter 24, Problem 1RQ

Leukocytes are differentiated white blood cells derived from either myeloid or lymphoid precursor cells. Cells of myeloid lineage include monocytes and granulocytes. Monocytes include macrophages and dendritic cells, specialized phagocytes that function as antigen-presenting cells (APCs) to initiate an adaptive immune response. Granulocytes include neutrophils, which are also phagocytes but not APCs, and mast cells, which are important inducers of the inflammatory response but may also cause allergic reactions. Lymphocytes include B and T cells, which facilitate adaptive immunity, and natural killer cells, which play a key role in destroying virus-infected and cancerous host cells.

What is the origin of the phagocytes and lymphocytes active in the immune response? Track the maturation of B cells and T cells.

Summary Introduction

Leukocytes (White blood cells) are derived from either myeloid or lymphoid precursor cells. Cells which are derived from myeloid lineage include monocytes and granulocytes. Monocytes comprise macrophages and dendritic cells which are specialized phagocytic cells called antigen presenting cells (APCs). Granulocytes include neutrophils and mast cells. Lymphocytes include B-cells (B leukocytes), T-cells (T leukocytes), and natural killer cells.

Explanation of Solution

Phagocytes are originated from the myeloid lineage and are specialized antigens presenting cells which help in developing adaptive immune responses in the body of an organism. These specialized cells comprise macrophages and natural killer cells. These phagocytic cells engulf and transport pathogen to the lymphocytes in order to generate an adaptive immune response. In contrast to this, lymphocytes originated from lymphoid lineage and comprise B-cells, T-cells, and natural killer cells.

B-cells mature and originate inside the bone marrow. B-cells are also specialized antigen presenting cells like those of macrophages and dendritic cells. In addition, these B-cells also act as a precursor of antibody-producing plasma cells. T-cells initially start their development process in bone marrow but they migrate to thymus cells for further maturation.