Topic 10: Eosinophil granulocytes, mononuclear phagocytes, thrombocytes Flashcards
What should be mentioned in this topic?
- Eosinophil Granulocyte
- Chemotaxis
- Antiallergic Effect
- Mononuclear Phagocyte
- Antigen Presentation
- Thrombocyte s /Plate le ts
Eosinophil Granulocyte
- 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.
Chemotaxis
- 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
Antiallergic Effect
- 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.
Mononuclear Phagocyte
- 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.
Antigen Presentation
- 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.
Mononuclear Phagocyte:
Enzymes in Granules:
- Proteases
- Myeloperoxidase
- Superoxid dismutase
- Acidic and alcalic phosphatise
Mononuclear Phagocyte:
Secretion of monocytes:
- loosening tissues with enzymes:
- collagenase
- elastase
- angiotensine convertase
- Stimulation of immune response:
- interleukin-1
- Interferon
- prostaglandins
Thrombocytes/Platelets
- 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
Enzymes in the Eosinophil granulocytes:
Enzymes:
- Histaminase,
- Aril-sulfatase,
- Myeloperoxidase,
- Acidic and alcalic phosphatise,
- Nuclease
Explain the mononuclear phaocyte systems:
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