Topic 10: Eosinophil granulocytes, mononuclear phagocytes, thrombocytes

Question 1

What should be mentioned in this topic?

Answer 1

• Eosinophil Granulocyte
• Chemotaxis
• Antiallergic Effect
• Mononuclear Phagocyte
• Antigen Presentation
• Thrombocyte s /Plate le ts

Question 2

Eosinophil Granulocyte

Answer 2

• Cells with diameter of 12-14micrometer.
• Nucleus is less segmented, red coloured granules are seen in the cytoplasm.
• These granules are actually lysosomes, containing enzymes. In horses the granules appear big,
  light and often covering the nucleus.
• their proportion in the blood increases during allergic processes and
• Granules: All red
  
  • In horses cover nucleus too
• Enzymes
  
  • Histaminase, Aril-sulfatase, Myeloperoxidase, Acidic and alcalic phosphatise, Nuclease
• Antiallergic Cells
• Lifetime
  
  • Circulation 3-8hrs
  • Tissues 3-5 days
• Smaller migrating capabilities than neutrophils
  
  • No phagocytosis, only pinocytosis
  • Stronger chemotaxic sensitivity.

Question 3

Chemotaxis

Answer 3

• WBC migrate towards higher concentration of specific signals.
• Most important chemicals:
  
  • Products of tissue breakdown
  • Histamine
  • Complement factors
  • Broken polysaccharide capsule of bacteria
• Chemotaxines produced by WBCs
• ECF-A (Eosinophil chemotaxis factor for anaphylaxis)
  
  • T-cells
  • Mast cells
  • Basophils

Question 4

Antiallergic Effect

Answer 4

• phagocytosis and form “respiratory burst”, but to a lesser degree than neutrophil granulocytes.
• Clears away metabolites produced by the basophil cells provoking inflammation and partly to
  assure the cellular elimination in parasites.
• Gather in inflammatory areas by chemotaxis.
• There are many kinds of enzymes in their granules out of which the role of histaminases and
  aril-sulphatase in removing the debris.
• The cell takes up and breaks down both the histamine produced by the basophil cells and the
  SRS-A that maintains inflammation for a long time.
• Able to degranulate. The most effective substances against parasites are the alcalic proteins
  produced by these cells.

Question 5

Mononuclear Phagocyte

Answer 5

• Biggest WBC 15-25micrometers.
• Big non segmented nucleus which is bean shaped.
• Cytoplasm contains asurophil granules where the degrading enzymes for the phagocytosed
  elements can be found.
• During the antigen-eliminatory processes the monocytes “present” the antigen to the other
  cells of the immune system. The secretory function of macrophages is also very important.
• Besides the intracellular digesting enzymes they produce extracellular enzymes, interleukin-1,
  interferons and prostaglandins.
• MPS: Mononuclear Phagocyte System
• MS: Macrophage system
  
  • RES: Reticulo endothelial system
  • RHS: Reticulo histiocytic system
  • Task: Antigen presentation, Secretion
• Cells with dividing capacity
  
  • Form polynuclear giant cells which has increased phagocytosis
• Lifetime
  
  • In circulation: 10-40hours
  • In tissues: 2-3 months
• Migration and Chemotaxis
  
  • Similar to neutrophil granulocytes
  • Circulating fraction is really small
  • Extravasal supply: tissue macrophages of significant importance.
• Granules
  
  • Small, non significant azurophyls o Enzymes
• Proteases
• Myeloperoxidase
• Superoxid dismutase
• Acidic and alcalic phosphatise
• Secretion of monocytes
  
  • loosening tissues with enzymes:
• collagenase
• elastase
• angiotensine convertase
  
  • Stimulation of immune response:
    
    • interleukin-1
    • Interferon
    • prostaglandins

Question 6

Antigen Presentation

Answer 6

APC cells manage to express the digested pieces of the phagocytised antigen together with their own MHC to the cell surface.
The adequate receptor of the helper T-lymphocyte (Th) recognises the piece of the antigen and the MHC complex. This initiates the immune system and finally leads to antibody production. This occurrence is called the antigen presentation.
Infected somatic cells manage to express foreign material to the cell surface too. This goes together with the MHC-I type surface marker. If MHCI plus an antigen complex occurs on the surface of the cell, it will be recognised by the cytotoxic T-lymphocyte receptors and the infected cell will be destroyed.

Question 7

Mononuclear Phagocyte:

Enzymes in Granules:

Answer 7

• Proteases
• Myeloperoxidase
• Superoxid dismutase
• Acidic and alcalic phosphatise

Question 8

Mononuclear Phagocyte:

Secretion of monocytes:

Answer 8

• loosening tissues with enzymes:
  
  • collagenase
  • elastase
  • angiotensine convertase
• Stimulation of immune response:
  
  • interleukin-1
  • Interferon
  • prostaglandins

Question 9

Thrombocytes/Platelets

Answer 9

• 1.5-3.5micrometers
• Lifetime: 5-10days
• Passive movement
• Found mainly in the circulation
• No nucleus, granular cytoplasm
  
  • Delta granules: calcium, serotonin and ADP
  • Alpha granules: coagulation factors
• Originate from a megacaryocyte
• Plasma membrane contain invaginations that form canaliculi systems
• Thrombocyte activating factors prompt the release of granules