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Blood Cells

White blood cells, including phagocytes like neutrophils and macrophages, play a crucial role in the body's immune response. Learn about their functions, production, and how they combat pathogens through phagocytosis. Explore innate immunity mechanisms like complement, inflammation, and fever.

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Blood Cells

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  1. Blood Cells

  2. White Blood Cells • Phagocytes - Neutrophils - Macrophages • Lymphocytes

  3. Phagocytes • Produced throughout life by the bone marrow. • Scavengers – remove dead cells and microorganisms.

  4. Neutrophils • 60% of WBCs • ‘Patrol tissues’ as they squeeze out of the capillaries. • Large numbers are released during infections • Short lived – die after digesting bacteria • Dead neutrophils make up a large proportion of puss.

  5. Macrophages • Larger than neutrophils. • Found in the organs, not the blood. • Made in bone marrow as monocytes, called macrophages once they reach organs. • Long lived • Initiate immune responses as they display antigens from the pathogens to the lymphocytes.

  6. Macrophages

  7. Innate Immune Responses • Innate immune mechanisms nonspecifically eliminate pathogens that invade internal tissues before they become established • Phagocytes • Complement • Inflammation • Fever

  8. Innate Immunity • Innate immune responses involve a set of general, immediate defenses against invading pathogens • Innate immunity includes phagocytic white blood cells, plasma proteins, inflammation, and fever

  9. Phagocytes • Macrophages • Large phagocytes that patrol interstitial fluid and engulf and digest pathogens • Secrete cytokines when receptors bind to antigen • Cytokines attract more macrophages, neutrophils, and dendritic cells to infection site

  10. Phagocytosis • If cells are under attack they release histamine. • Histamine plus chemicals from pathogens mean neutrophils are attracted to the site of attack. • Pathogens are attached to antibodies and neutrophils have antibody receptors. • Enodcytosis of neutrophil membrane  phagocytic vacuole. • Lysosomes attach to phagocytic vacuole  pathogen digested by proteases

  11. Phagocytosis • Stages in phagocytosis • Phagocyte detects chemicals released by a foreign intruder (e.g. bacteria) • Phagocyte moves up the concentration gradient towards the intruder • The phagocyte adheres to the foreign cell and engulfs it in a vacuole by an infolding of the cell membrane. • Lysosomes (organelles which are rich in digestive enzymes & found in the phagocytes cytoplasm) fuse with the vacuole & release their contents into it.

  12. Phagocytosis • The bacterium is digested by the enzymes, and the breakdown products are absorbed by the phagocyte. • During infection, hundreds of phagocytes are needed. • Pus is dead bacteria and phagocytes!

  13. Phagocytosis

  14. Pus An accumulation of : - • dead phagocytes • destroyed bacteria • dead cells

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