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.

• Lifetime:
• Circulation 3-8hrs
• Tissues 3-5 days
• 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

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
  assure the cellular elimination in parasites.
• Gather in inflammatory areas by chemotaxis.
• 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 is very important.
- Besides the intracellular digesting enzymes they produce extracellular enzymes, interleukin-1,
interferons and prostaglandins.

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.

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

Question 10

Enzymes in the Eosinophil granulocytes:

Answer 10

Enzymes:

• Histaminase,
• Aril-sulfatase,
• Myeloperoxidase,
• Acidic and alcalic phosphatise,
• Nuclease

Question 11

Explain the mononuclear phaocyte systems:

Answer 11

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