L8: Innate Immunity - The Cells Flashcards
Cells of the innate immune system are derived from which lineage?
The myeloid lineage.
Describe the 4 key steps involved in the process of inflammation.
- Vasodilation - increased blood flow, reduction of velocity. Characterises heat and redness.
- Endothelial cells lining the blood vessels are activated to express cell-adhesion molecules that allows leukocytes to attach and migrate into the tissues = extravasation.
- Increase in vascular permeability allowing fluid and plasma proteins to enter the tissue, resulting in edema (swelling) and pain.
- Clotting in microvessels at site prevents the spread of the pathogen via the blood.
Inflammation plays 3 main roles in combating infection. Name them.
- Delivery of effector cells to the site of infection.
- Blood clotting to prevent the spread of infection.
- Repair of injured tissue.
Three types of granulocytes?
Basophils, neutrophils and eosinophils.
4 key types of innate immune cells?
Neutrophils, macrophages, dendritic cells and innate lymphoid cells (ILCs).
Basic facts about neutrophils.
- They are polymorphonuclear - nucleus with several lobes.
- Granulocytes.
- Most abundant type of wbc.
- They are recruited to the site of infection or injury.
- They kill pathogens through phagocytosis, degranulation or through neutrophil extracellular traps.
- They show the greatest phagocytic activity out of all the granulocytes.
Which innate immune cells perform phagocytosis?
Macrophages and neutrophils.
What initiates phagocytosis?
Initiated when opsonins are recognised on targets.
5 key steps of phagocytosis.
- Microbe attaches to the phagocyte p.membrane + is engulfed.
- Engulfed into a phagosome.
- Lysosomes recruited.
- Fusion forms a phagolysosome.
- Lysosome contents are released to destroy the pathogen. Contents include reactive oxygen species, defensins and hydrolytic enzymes.
Explain the process of degranulation.
Azurophilic (primary) and specific (secondary) granules fuse with the phagosome and release their contents: proteases, defensins and reactive oxygen species.
What are neutrophil extracellular traps?
Networks of extracellular fibres primarily composed of DNA and antimicrobial proteins such as histones and neutrophil elastase. They trap and kill bacteria.
Where are macrophages found?
Reside in tissues, e.g. Microglia are found in the brain, osteoclasts are found in the bone.
Macrophages mature continuously from ______, found in the bloodstream.
Monocytes.
Main functions of macrophages?
- Phagocytose and destroy pathogens in the tissues.
- Secrete cytokines that contribute to the inflammatory response.
- Present antigens to T cells.
- Contribute to tissue repair.
Why are DCs slightly different in comparison to other innate immune cells?
They arise from both myeloid and lymphoid progenitors.
Those from the myeloid = conventional DCs (cDCs).
Those from the lymphoid = plasmacytoid DCs (pDCs).
