Module 2 Unit 1: Nonspecific and innate defense mechanisms Flashcards
Defends the body against microbes during the first few hours or days after infection
Innate Immunity
Mediated by mechanisms that are in place even before infection and facilitate rapid responses to invading microbes
Innate Immunity
Cardinal feature of the adaptive immune system
Memory
TRUE or FALSE: The adaptive immune system does not remember prior encounters with microbes and resets to baseline after each encounter
FALSE
Innate Immune System
This type of immunity develops as a response to infection and adapts to the infection
Adaptive Immunity
Recognizes and reacts to a large number of microbial and nonmicrobial substances (antigens)
Adaptive Immunity
Phagocytes express receptors for bacterial endotoxin known as _______ and other receptors for ________, which are present in bacterial cell walls
Lipopolysaccharide (LPS), Peptidoglycans
Phagocyte receptors also recognize ________ in bacterial glycoproteins
Terminal mannose residues
Microbial molecules that stimulate innate immunity
Pathogen-associated molecular patterns (PAMPs)
Receptors of innate immunity that recognize shared structures
Pattern recognition receptors (PRRs)
TRUE or FALSE: The components of innate immunity have evolved to recognize structures of microbes that are often essential for the survival and infectivity of microbes
True
These are molecules recognized by the innate immune system that are released from damaged or necrotic host cells
Damage-associated molecular patterns (DAMPs)
2 specific receptors in the adaptive immune system capable of recognizing millions of antigens
Immunoglobulin (Ig)
T cell receptors (TCRs)
Cells capable of recognizing self-antigens in the adaptive immune system
* They die or are inactivated on encounter with self-antigens
Lymphocytes
3 strategies done to deal with threats posed by microbes
- Avoidance
- Resistance
- Tolerance
This mechanism prevents exposure to microbes and includes both anatomic barriers and behavior modifications
Avoidance mechanism
Aimed at reducing or eliminating pathogens
Resistance
Molecular and cellular functions suited to resist diff. categories of pathogens
Mediators or effector mechanisms
Responses that enhance a tissue’s capacity to resist damage induced by microbes
Tolerance
Defenses provided by specialized cells that have the ability to recognize, sequester, and eliminate various types of organisms or harmful substances
Cell-mediated immunity
Cell-free defenses provided by soluble macromolecules that circulate in the blood and extracellular fluid, and are inhospitable to foreign invaders
Humoral immunity
Earliest defense mechanism active at the portals of entry, providing physical barriers and antimicrobial molecules and lymphoid cells
Epithelia
Microbes that breach epithelia, as well as dead cells in tissues, are detected by
Macrophages
Dendritic cells
Mast cells
Initiate the process of inflamm.
Cytokines
These react against microbes and promote their destruction
Plasma proteins
These are produced by viruses; inhibit infection of other cells and the killing of infected cells by NK cells
Interferons
General Features of Innate Immunity
Barrier defense Complement activation Pattern recognition Inflammation Phagocytosis Target cell lysis
These take action once invaders breach the barriers as a result of pattern recognition mediated by the binding of PRMs to PAMPs furnished by pathogens and to DAMPs emanating from damaged host cells
Innate leukocytes
PRMs expressed by innate leukocytes
Pattern recognition receptors (PRRs)
PRRs are located in the _____ of an innate leukocyte, or are soluble molecules free in the leukocyte’s cytoplasm, or are fixed in the membranes of _____
plasma membrane, endosomes
These activate events responsible for the influx of innate and adaptive leukocytes into the site of injury or infection
Proinflammatory cytokines
TRUE or FALSE: Like acute inflammation, chronic inflammation is a normal process, so there is nothing to worry about and will reside on its own.
False
Prolonged inflammation is immunopathic and undermines homeostasis
Phagocytosis translates to
“eating of cells”
Phagocytosis is carried out by 3 types of PRR-expressing cells namely
Neutrophils
Dendritic cells
Macrophages
_____ and _____ engulf pathogens, dead host cells, cellular debris, and host macromolecules
Macrophages, Dendritic cells
Cells that carry out target cell lysis
Neutrophils
Macrophages
NK cells
Cancer cells and infected cells express these components on their surfaces that mark them as target cells for destruction
DAMPs and/or PAMPs
A phospholipid-based substance made in the lung that acts to trap microbes and can directly lyse bacteria
Pulmonary surfactant
A prominent enzyme in tears and saliva that breaks down peptidoglycan in the cell walls of gram-positive bacteria
Lysozyme
Lysozymes lack _____, making them a prototype of an innate immune protein since they do not affect host cells
Peptidoglycan
Lysozyme is made by
epithelial cells, phagocytes, and Paneth cells
An ancient form of defense because they are found in most species
Antimicrobial peptides
3 classes of antimicrobial peptides
- Defensins
- Catelicidins
- Histatins
Key property of defensins
* Underly their specificity for pathogenic membranes
Amphipathicity
30-40 amino acid peptides that have 3 disulfide bonds
Defensins
Alpha defensin produced by Paneth cells
Cryptidins
Neutrophils produce _____ and store them in primary granules
alpha-defensins
Type of defensin made in the urogenital and respiratory tracts, skin, and tongue
beta-defensins
Antimicrobial peptide class that lacks disulfide bonds in the alpha-defensins
Cathelicidins
Antimicrobial peptide class produced by epithelial cells, phagocytes, and keratinocytes
Cathelicidins
Antimicrobial peptide class produced in the parotid, sublingual, and submandibular glands in the oral cavity
Histatins
Histidine-rich and target fungal membranes
Histatins
A small protein of the S-100 family with potent antimicrobial activity against E. coli
Psoriasin
S-100 protein that kills S. aureus
* related to psoriasin
Calprotectin
Bind carbohydrates on bacterial cell walls, preventing them from contacting the intestinal epithelial cells; are also directly bactericidal
RegIII proteins
2 surfactant proteins that are members of a class of microbe-binding proteins (collections); present in the lungs and secretions of other mucosal epithelia
SP-A & SP-D
Prevent infection by blocking and modifying surface components and promoting pathogen clearance
SP-A & SP-D
Binds the complex polysaccharides coating many of the capsulated forms
* Klebsiella pneumoniae
SP-A
Binds the exposed cell wall lipopolysaccharide of the non-encapsulated form
* Klebsiella pneumoniae
SP-D
