Immune System Cells: Mononuclear Phagocytes

Mononuclear Phagocytes

• Originate in bone marrow (BM) and enter peripheral blood as monocytes
• Mature into macrophages (histiocytes) in tissues
• 0.2 – 0.8 x 10^9/l, 12 – 17 mm diameter, oval – kidney bean shaped nucleus
• Monocyte life span in blood = few days, macrophages can live for years in tissues

Functions of Macrophages（mono的長大版）

• Phagocytosis of foreign particles吞噬外来颗粒
• Production of inflammatory mediators
• Antigen presentation to T cells, initiating an adaptive response
• Mediate both innate and adaptive responses
• in the CNS - microglia
  in the liver - Kupffer cells
  in the lungs - alveolar macrophages
  in the kidney - mesangial cell.

Dendritic Cells

• Accessory cells inducing adaptive response

• Found in most organs and epidermis of skin

  (Interdigitating dendritic cells=Langerhans cells)

• Function: pick up antigens, transport to lymph nodes, and present to T cells

• Mediate adaptive responses.

• Follicular dendritic cells - restricted to lymphatic tissue.

• Do not originate in BM.

• Unrelated to interdigitating dendritic cells.

Granulocytes

• Contain abundant cytoplasmic granules
• Include neutrophils, eosinophils, and basophils

Neutrophils (Polymorphonuclear Leukocytes)

• Multi-lobed (3 – 5 lobes usually) morphologically diverse nuclei
• Most abundant granulocyte (2.5 – 7.5 x 10^9/l)
• 12 – 15 mm diameter, life span 10 h (blood), days in tissues
• Highly phagocytic, key cells in anti-bacterial responses, mediate innate response and support adaptive responses

Eosinophils

• Bi-lobed nucleus and acidophilic granules
• 0.04 – 0.4 x 10^9/l, life span = 2 weeks
• Acidic staining granules containing major basic protein
• Function primarily in the elimination of infectious agents such as helminth worms.
• Mediate hypersensitivity (allergic) reactions – mediate adaptive responses.

Basophils

• Basophilic granules.
• Dark basic staining granules containing heparin and histamine – stain purple
• 0.01 – 0.1 x 109/l
• Mediate hypersensitivity reactions through release of chemicals such as histamine
• Support mast cells in tissues and mediate allergic reactions – mediate adaptive responses

This quiz covers the characteristics and functions of mononuclear phagocytes, including monocytes and macrophages, which are crucial cells of the immune system. Learn about their origin, development, and lifespan.