Innate Immunology Flashcards
What is blood composed of?
55% plasma: proteins (including antibodies/immunoglobin), other solutes and water
45% formed elements: platelets, white blood cells (leukocytes), red blood cells
What do bone marrow stem cells form?
They are a source of blood cells (hematopoiesis)
Derived from hematopoietic stem cells in bone marrow:
Myeloid:
- red blood cells (erythrocytes)
- white blood cells: granulocytes, monocytes, dendritic cells, platelets (innate immune cells)
Lymphoid:
- white blood cells: B and T lymphocytes (adaptive immune cells)
Describe granulocytes in blood
Neutrophils: 75% of all leukocytes, highly phagocytic “eat and kill” - numbers in blood increase during infection
Granulocytes circulate in the blood and can move into tissue during inflammation - and do their eat and kill job
Describe granulocytes in tissue
Mast cells
- Mast cells line mucous surfaces (not found in blood)
- Release granules that attract white blood cells to areas of tissue damage
Describe the phagocytic cells (Monocytes and Macrophages)
Monocytes:
- Monocytes present in blood - low phagocytosis
- Leave blood - develop into macrophages in tissues eg. spleen, liver - high phagocytosis
Macrophages:
- Macrophage become resident (sessile - not moving, established in that tissue) or move through tissues (migratory)
- 3 important functions:
1. Phagocytosis (professional eaters)
2. Release of chemical messengers (that communicate with other cells that there is an infection going on)
3. Show information about phathogenic microbes to T cells (linking innate and adaptive immunity)
Describe dendritic cells: linking innate and adaptive immune responses
- Dendritic cells are found in low numbers in blood and all tissues in contact with the environment
- Phagocytic
- Most important cells type to help trigger adaptive immune responses
- So few of them because they are so potent and can do their job well in very small numbers
How do cells of the immune system move around the body?
- Cells are carried in the blood and in the lymph
- Cells can leave blood to enter tissues
- Lymph in tissues collects into lymphatic vessels. These drain lymph into lymph nodes.
How do innate cells recognise pathogens?
Pathogen-associated molecular patterns - The immune system uses common building blocks to recognise what belongs in the body and what doesn’t.
What are the common building blocks of viruses and bacteria?
Viruses:
- Nucelic acids: ssRNA and dsRNA
Note: SARS-Cov-2 is an example of an ssRNA from a virus
Bacteria:
- Cell wall: lipopolysaccharide (LPS)/endotoxins, lipoteichoic acid
- Flagella: flagellin
- Nucleic acid: unmethylated CpG DNA
Describe how fever/pyrexia works in the body
- Abnormally high temperature >37*C
- Re-setting of thermostat (hypothalamus)
- Pyrogens - released by cells of the immune system
- Phagocytes produce the chemical messenger and pyrogen interleukin-1 (IL-1) after ingesting bacteria
(Pyrogen is the chemical messenger, which can reset the hypothalamus, telling it that the body needs to be at a higher temperature) - Why might fever be useful?
- Can inhibit bacterial replication
- Some factors of the immune system can work more effectively at a higher temperature - decrease in phagocytosis leads to decrease in IL-1 to which leads to decrease in temperature
Describe how pattern recognition receptors work
- Found on the surface of innate immune cells
- If the building block is on the outside of the cell it will bind there
- If the building block is inside a virus or something it will get phagocytose and brought into the cell, where once the virus has been broken down, the building block can bind to toll-like receptors
- Once it is bound, a message is sent to the nucleus, telling it to regulate gene transcription, to up regulate the production of chemical messengers. The chemical messengers then leave the cell and communicate with other cells.
