Cells of Innate Immunity Flashcards
PAMPs
pathogen-associated molecular patterns. diverse mixture of molecules expressed by microbial invaders that can be recognized by the body as foreign.
DAMPs
damage-associated molecular patterns. molecules released from damaged cells, generate alarm signals
PRRs
Pattern-Recognition Receptors. PAMPs and DAMPs bind to them. They are found on sentinel cells located in blood, on cell surfaces, and within cells (either in endosomes or in cytoplasm)
Binding to pattern-recognition receptors
- triggers inflammation
- triggers interferon production
- triggers sickness behavior
- begins the adaptive immune process
TLRs
Toll-like receptors.
TLRs found on cell surfaces
detect microbial cell surface molecules. primarily directed against bacteria
TLRs found in intracellular vesicles
detect foreign nucleic acids. primarily directed against viruses
Leukocytes
WBC. originate from the hematopoietic cells in the bone marrow
Most common Leukocytes
- Neutrophils
- Lymphocytes
- Monocytes
- Eosinophils
- Basophils
Neutrophils
the first phagocytic cells to attack and destroy invading bacteria. Move rapidly but lack stamina. Simply destroy invaders but can cause collateral damage. Kill using reactive oxygen compounds and defensins. Rapidly mobilized from the bone marrow
Neutrophils Leaving blood vessels
in inflamed tissues the blood vessel walls are sticky. Neutrophils stick to vascular endothelium. Adherence is mediated by integrins and selectins
Mononuclear Phagocytes
arise primarily from the marrow and are released into the blood as monocytes. They may circulate for hours to a few days before entering the tissues and differentiating to become macrophages.
Granulocytes
have a segmented nucleus and are classified according to their staining characteristics as neutrophils, eosinophils, or basophils
Stages of Phagocytosis
- chemotaxis
- adherence
- ingestion
- destruction
Opsonization
bacteria coated by antibodies and/or complement bind to neutrophil receptors and are readily ingested
NETosis
extracellular net (neutrophil extracellular trap) consisting of sticky DNA containing multiple antibacterial molecules. These nets capture and kill microorganisms without ingesting them
Respiratory Burst
neutrophils generate hydrogen peroxide and bleach when they capture bacteria. Binding of bacteria allows NADPH-oxidase to assemble and generate singlet oxygen. Singlet oxygen interacts with water to produce hydrogen peroxide and with chloride ions to generate hypochloride
Neutrophil Granules
release their contents during phagocytosis. Contain antimicrobial molecules such as defensins. Contain enzymes that can break down tissues and so enable neutrophils to reach the invaders
Macrophages
move slowly but are more powerful phagocytes. Can kill bacteria that defeat neutrophils. Can be activated. Also trigger tissue repair and wound healing. Located in tissues and bloodstream
Macrophage Names
brain- microglia
liver- Kupffer cells, histiocytes
blood- monocytes
lungs- alveolar macrophages
M1 cells
aggressively phagocytic. Loaded with NOs and proteases. Secrete proinflammatory cytokines. Activated in 2 stages. Activated in such a way that their destructive abilities are enhanced. They produce nitric oxide
M2 cells
trigger wound repair and healing. Secrete antinflammatory cytokines. Alternatively activated and serve to remove dead and dying cells and repair
TLR5
Location: cell surface
Ligand: flagellin
Pathogen Recognized: bacteria
Important PRRs
collectins/lectins, TLRs, and complement
TLR 4
Location: cell surface
Ligand: lipopolysaccharide
Pathogen Recognized: bacteria and viruses
What are the innate immune cells
Neutrophils, eosinophils, basophils, mast cells, NK cells, innate lymphoid cells, macrophages, dendritic cells
What mediates rolling and adherence to get neutrophils out of blood vessel?
L selectin and P selectin
What mediates adherence and emigration?
LFA-1 and ICAM-1
Collagenase
degrade bacteria and tissues
Gelatinase
degrade bacteria and tissues
Myeloperoxidase
respiratory burst
Contents of neutrophil granules
collagenase, gelatinase, myeloperoxidase, lysozyme, defensin
