Questions and Answers
TLR3 recognizes dsRNA, a component of viral replication.
True
TLR1 and TLR6 are involved in recognizing diacyle peptides produced by Mycoplasma.
True
TLR5 recognizes bacterial flagellin, a protein component of bacterial flagella.
True
TLR2 recognizes lipopolysaccharide (LPS), a component of Gram-negative bacteria.
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NOD-like receptors are located on the cell surface and detect extracellular microbial products.
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Phagocytic cells, like macrophages, are responsible for engulfing and destroying pathogens.
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The activation of the NF-ҡB pathway by NOD-like receptors leads to an anti-inflammatory response.
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TLR10 recognizes a specific type of bacterial or viral component.
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The first line of defense against pathogens is entirely nonspecific, meaning it does not target particular pathogens.
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The presence of a normal microbiota in the gastrointestinal tract is considered a component of the first line of defense.
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Lysozyme is an antimicrobial enzyme found only in tears and saliva.
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Skin is considered a physical barrier to pathogens due to its ability to produce sweat and sebaceous secretions with antimicrobial properties.
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Psoriasin, a protein with antibacterial properties, is produced by the digestive system.
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The acidity of the stomach is a key factor in the first line of defense against pathogens.
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Ciliated cells in the respiratory tract move mucous upwards towards the natural orifices to prevent pathogens from entering the body.
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The immune system's adaptive response, which involves specific recognition of pathogens, is considered part of the first line of defense.
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Study Notes
Innate Immunity
- Innate immunity is the first line of defense against pathogens and provides immediate response
- It is a general defense mechanism that is not directed against specific pathogens
- Innate immunity is active from birth and lacks immunologic memory
Barriers to Infectious Agents
- Skin (epithelium) and mucous membranes are physical barriers that prevent pathogen entry
- Sweat and sebaceous secretions have antimicrobial properties due to acid pH and fatty acids
- Lysozyme, a hydrolytic enzyme, is present in mucous secretions and can lyse gram-positive bacteria
- Psoriasin, a protein with antibacterial properties, is produced by skin
Respiratory Tract Defense
- Mucous covers the surface and is constantly being driven upward by ciliated cells towards natural orifices
- Lysozymes, IgA, and phagocytes provide additional defense mechanisms
- Hair at the nares and cough reflex serve as special protective mechanisms
Gastrointestinal Tract Defense
- Saliva contains hydrolytic enzymes
- Acidity of the stomach and proteolytic enzymes in the small intestine provide defense
- Normal microbiota in the gut opposes the establishment of pathogenic microorganisms through bacterial interference
- Normal Lactobacilli in the vagina maintain acid pH, inhibiting yeast, anaerobe, and Gram-negative bacteria growth
Innate Immune Response
- Interaction with invading microorganisms triggers the release of complement, cytokines, and chemokines
- Macrophages and other phagocytic cells possess microbial sensors, including TLRs, NLRs, and RIG-1 like helicases
- TLRs recognize pathogen-associated molecular patterns (PAMPs) and initiate the innate immune response
- 10 human TLRs have been identified, each recognizing unique microbial patterns
- NOD-like receptors sense DAMPs and PAMPs in the cytosol and activate the NF-ҡB pathway
Phagocytic Cells
- Phagocytic cells include macrophages and other cells that can engulf and kill microorganisms
- Functions of phagocytic cells include chemotaxis, migration, ingestion, and microbial killing
- Phagocytic cells can increase in number during infections and engulf foreign substances in lymphatic, lung, or blood stream
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Description
This quiz covers the first line of defense against pathogens, including barriers to infection and immune components that aid in the adaptive response. It discusses the general defense mechanisms that are present from birth and are rapidly mobilized at the initial site of infection.
