Phagocytosis Flashcards
Russian scientist, observed that foreign objects introduced into transparent starfish larvae became surrounded by motile cells that attempted to destroy these invaders, a process called phagocytosis.
Elie Metchnikof
initiated as a result of tissue damage, either trauma or as a result of microorganism
multiplication
Phagocytosis
has increase surface receptors that allow for adherence
Activated phagocyte
Process by which cells tend to move in a certain direction under the stimulation of a chemical substances such as opsonin (Examples are Antibodies, CRP, and complement components)
Chemotaxis
whereby cells are attracted to the site of inflammation by chemical substances(chemotaxins) such as soluble bacterial factors or acute-phase reactants including complement components and CRP
Chemotaxis
Without the influence of these chemotactic substances, cell motion is random
Chemotaxis
Diseases associated with abnormal chemotactic activity
Job syndrome / Hyperimmunoglobulinemia E
Disease associated with abnormal random and chemotactic activity
Lazy Leukocyte syndrome
Migration is toward to the site of stimulation
Positive chemotaxis
Migration away from the site stimulation
Negative chemotaxis
physical contact between the phagocytic cell and the microorganism occurs, aided by opsonins.
Adherence
microorganism is completely surrounded by a part of the cell membrane
Formation of phagosome
cytoplasmic granules fuse with membrane of phagosome, emptying contents into this membrane-bound space.
Formation of the phagolysosome
Digestion of the microorganism by
hydrolytic enzymes
Excretion of contents of phagolysosome to the outside by
exocytosis
via Pattern Recognition Receptors (PRRP) that recognize lipid and carbohydrates sequences on microorganisms
Direct phagocytosis
via Opsonin receptors that recognize opsonins such as IgG, C3b bound to microorganism
Indirect phagocytosis
The Reduction of Oxygen that Leads to the formation of superoxide anion, hydroxyl radicals, hydrogen peroxide and hypochlorite ions
Oxygen dependent/Respiratory Burst
Oxygen dependent/Respiratory Burst reduce oxygen by the help of enzymes
NADPH oxidase, Superoxide dismutase (SOD), and Myeloperoxidase
Production of nitric oxide from oxidation of L-arginine by NO synthase
Oxygen Independent
Oxygen Independent is the Production of nitric oxide from oxidation of L-arginine by NO synthase which is produced by
Interferon Gamma activated cells.
Oxygen independent produces
Lysozyme, lactoferrin, Major basic proteins, lipase & defensins
Phagocytosis can be divided into six stage
Chemotaxis -> adherence -> engulfment ->phagosome formation -> fusion -> digestion and destruction
Fusion of the phagosome with lysosomal granules creates a
phagolysosome
Phagocytic cells
Dendritic cells (most potent), Monocytes/Macrophages, Neutrophil, Basophil, and Eosinophil
The most potent/lethal bactericidal product formed in the respiratory burst
Hydrogen peroxide
Known to be central to the killing of microbes, because its dysfunction causes chronic granulomatous disease.
NADPH oxidase
Patients with this disease suffer from recurring, severe bacterial infections
NADPH oxidase
A lytic enzyme from the lysosomal granules that are able to cleave segments of bacterial cell walls without the benefit of oxygen.
Defensins
They are chemical messengers that cause cells to migrate in a particular direction
Chemotaxins
Produced by neutrophils, certain macrophage populations, and Paneth cells of the small intestine. This class of defensins is believed to disrupt the microbial membrane.
Alpha defensins
Produced by neutrophils as well as epithelial cells lining the various organs, including the bronchial tree and genitourinary system. They are believed to increase resistance of epithelial cells to colonization
Beta defensins
Surface receptors that promote cell to cell interaction. It is an adhesion molecule together with selectins
Integrins
Bactericidal and viricidal protein in the presence of C3 component and magnesium
properdin
Heat stable cationic substance released by platelet during coagulation
Beta-Lysin
Iron binding protein that is found in secretory fluid such as milk, saliva, tear, and nasal secretion. It is also released as a secondary granules of PMNs.
Lactoferrin
It protect against bacterial infection, possibly by preventing the growth of bacteria by depriving them of essential nutrients (iron) or by killing bacteria by destroying their cell walls
Lactoferrin
Three groups of PRRs exist
Secreted PRRs
Phagocytosis receptors
Toll-like receptors (TLRs)
are molecules that circulate in blood and lymph; circulating proteins bind to PAMPs on the surface of many pathogens. This interaction triggers the complement cascade, leading to the opsonization of the pathogen and its speedy phagocytosis
Secreted PRRs
are cell surface receptors that bind the pathogen, initiating a signal leading to the release of effector molecules (e.g., cytokines)
Phagocytosis receptors
_____ have cell surface receptors that recognize PAMPs containing mannose.
Macrophages
are a set of transmembrane receptors that recognize different types of PAMPs they are a set of transmembrane receptors that recognize different types of PAMPs
Toll-like receptors (TLRs)
recognizes teichoic acid and peptidoglycan found in gram-positive bacteria
TLR2
recognizes lipopolysaccharide found in gram-negative bacteria
TLR4
recognizes lipoprotein found in mycobacteria
TLR1
recognizes bacterial flagellin
TLR5
Refers The overall reaction of the body to injury or invasion by an infectious agent
INFLAMMATION
The cardinal signs of inflammation
a. Rubor - redness(erythema) *first sign
b. Dolor- pain
c. Calor – Heat
d. Tumor – Swelling (edema)
e. Function laessa – loss or diminished function
acts to combat the early stages of infection and also begins a process that repairs tissue Damage.
acute inflammatory response
The predominant WBC found is
neutrophil
The Predominant Cells found in chronic inflammation are
monocytes/macrophages.
