Innate Immunity Flashcards
Innate defense
- You can produce prior to exposure by a specific pathogen
- Does not require change to DNA/genes
- All organisms have a form of innate immunity
Innate immunity consist of…
- Inflammatory response
- Cells (such as leukocytes) and molecules
- Complement system
Adaptive immunity consist of…
- B cells
- T cells
External immunity
- Barriers that prevent pathogens from entering body
- Skin, hair, cilia
- Mucus membranes
- Chemical secretions
Internal immunity
- Body’s defenses once pathogen is inside
- Inflammatory responses
- Complement proteins
- Phagocytic cells
- NK cells
Layers of the skin?
Epidermis, dermis, and hypodermis
Mucous membranes
- Trap pathogens that enter through skin
- Secrete lysozymes
Lysozymes
- In mucous membranes
- Antimicrobial proteins that nonspecifically break down bacterial cell walls
Sebaceous glands
- In skin
- Produces oil/sebum as a physical barrier to pathogens
Cilia
- Hair-like projections in respiratory tract
- Sweep away pathogens
Stomach acid
Gastric acid kills many microbes with low pH
Symbiotic bacteria
Help keep us alive by out-competing other hostile bacteria
Inflammatory response
- Happens if physical barrier is broken
- Injury site reddens and swells up
Mast cells
- Sound the alarm
- WBCs that sit in the tissue
- Once injury happens, injured cells and mast cells produce histamine
Histamine
- Dilates nearby capillaries and make capillary walls more permeable
- Immune cells can get to site of injury
- Increases blood flow in capillaries
Swelling
From permeable capillaries, blood vessels become leaky and fluid starts accumulating in nearby tissues
Pain from inflammation
Swollen areas exert pressure on free nerve endings, continuous pain
SLIPR
- Swelling
- Loss of function
- Increased heat
- Pain
- Redness
Fever
- Turned on/off by brain, systemic response
- Body temperature increases to hinder growth and kill pathogens
Functions of inflammation
- Elimination of the initial cause of infection or cell injury
- Clearance of damaged cells
- Initiation of tissue repair
Diapedesis
- Process of cells moving from capillaries to tissues
- Happens at site of injury
Chemotaxis
Moving to a location in response to a chemical signal
WBCs go to injury site because of…
Chemical signals
Cells of the innate immune system include…
- Granulocytes
- Monocytes/macrophages
- Dendritic cells
- Mast cells
- Natural killer cells
Platelets
- No nucleus, called anucleate
- Helps activate immune system
Platelet functions include…
- Regulate the regulation/ maturation of macrophages, neutrophils, and dendritic cells
- Act as immune system’s first responder when foreign entities enter bloodstream
Granulocytes
Leukocytes that have granules that contain antimicrobial molecules, like enzymes and proteins
Granulocytes include…
- Neutrophils
- Eosinophils
- Basophils
- Mast cells
5 main types of leukocytes are…
- Neutrophils: Highest number
- Lymphocytes
- Monocytes/macrophages
- Eosinophil
- Basophils: Lowest number
Mnemonic for number of leukocytes circulating in blood from highest number to lowest number
Never Let Monkeys Eat Bananas
Most numerous leukocyte?
Neutrophils, 40-70%
Neutrophils
- One of the first cells recruited to inflammation site
- Phagocytes: Eat and destroy pathogens
Lymphocytes
- Identify and acquire target before killing it
- Three types: B cells, T cells, NK cells
NK cells
- Innate response
- Attack and kill virus infected cells or cancerous body cells
What are NK cell’s two main weapons?
Perforin and granzymes
Perforin
Pokes holes in pathogenic cell membranes, leads to cell lysis
Granzymes
Proteases stimulates a target cell to undergo apoptosis, useful for killing cancer cells
Monocytes
In the blood vessels
Macrophages
In infected tissues
Monocytes/macrophages functions?
- Phagocytes that eat pathogens nonspecifically
- Later serve as antigen-presenting cells to activate adaptive immunity
Eosinophils
- Cytoplasms are filled with granules which contain proteins that are released to kill pathogens
- Effective against parasites
Least numerous leukocyte?
- Basophils
- Less than 1%
Basophils
Contains granules that can be released to nearby tissues, includes histamine and heparin
Heparin
- In granules of basophils
- Are anticoagulants, prevents blood from clotting too quickly
Basophils vs mast cells?
- Basophils leave bone marrow as mature cells and circulate in blood
- Mast cells leave bone marrow and circulate in blood as immature cells, mature when they enter tissue
Dendritic cells
- Pinocytosis while surveilling the tissue
- Phagocytosis when pathogen is detected
- Antigen presenting cells: Go to lymph nodes to activate adaptive immunity
What do macrophages and dendritic cells use?
- Toll like receptors to recognize microbes
- Triggers phagocytosis and other elements after binding occurs
How do innate immune cells recognize invaders?
Pattern-recognition receptors
MAMPs
Microbe associated molecular patterns
PAMPs
Pathogen associated molecular patterns
Pattern-recognition receptors bind to what to stimulate innate immunity and inflammatory responses?
MAMPs
DAMPs
Damage associated molecular patterns
What do DAMPs do?
- Endogenous stress signals when inflammation is induced by noninfectious causes such as trauma
- Act as generic markers for cell damage or death by binding and activating PRRs
Toll like receptors (TLRs)
- Innate immune system
- Most studied PRR family
- Senses distinct types of MAMPs, thus conferring a degree of specificity to the innate response
Nucleotide binding oligomerization domain (NOD) like receptors (NLRs):
Recognize a wide variety of MAMPs and DAMPs
RIG-I like receptors
- Expressed by both immune and nonimmune cells
- mediate antiviral responses by inducing the production of type I and III interferons and proinflammatory cytokines
Interferon
- Molecule released by virus infected cells to warn nearby non-infected cells
- Binds to non-infected cells to help them prepare for viral attack
What cells do interferons activate?
- Dendritic cells
Complement system
System of blood plasma proteins that help immune cells fight pathogens more effectively
Complement system’s functions include…
- Destruction of invaders
- Signaling of immune system
How is the complement system activated?
Proteins turn each other on through a cascade series of activation
Effects of the complement system?
- Improves the eating ability of phagocytosis cells, opsonization
- Amplifying inflammatory responses
- Lysing pathogen membranes
Opsonization
Bind complement protein C3b to antigens, tags them for phagocytosis
Membrane attack complex (MAC)
- MAC proteins group on the pathogen membrane
- Salt and fluids enter the pathogen
- Pathogen swells then bursts
Antigen
- Bacteria, viruses, fungi, etc.
- “Antibody generating”
Antibody
Protein produced by immune system to attach and fight off antigens
Classical pathway
Antigen dependent
Antibodies involved in classical pathway?
IgG or IgM
Steps of classical pathway
- Antigen comes into body, make antibodies IgG or IgM
- Activates C1 complex - activated complement system here, classical pathway ends
- Starts cascade, turns on proteins and cleaves them
- C3 cleaves into C3b
How is the lectin pathway activated?
After the recognition and binding of pathogen associated molecular patterns (PAMPs) by mannose-binding lectin (MBL)
What does the lectin pathway activate?
C4, C2, and C3
What is different about the lectin pathway from the classical pathway?
Uses lectin instead antigen antibody complex
Alternative pathway
Initiated by low-level activation of C3 via its hydrolysis (C3b)
What is different about the alternative pathway from the classical pathway?
Goes straight to C3, skips antigen-antibody complex
Put the following items in chronological order: Inflammatory chemicals, phagocytosis, chemotaxis, margination, diapedesis
- Inflammatory chemicals
- Margination: Clinging to capillary walls of injury
- Diapedesis: Squeeze through the capillary walls
- Chemotaxis: Going to the chemicals
- Phagocytosis: Eat pathogens
What physical/chemical barrier secretes lysosomes?
Mucous membranes
Does an infection need to be present to cause inflammation?
No
What happens when you take an antipyretic?
Downregulating inflammatory response
Antipyretic
Anti-fever
What substance do basophils secrete to prevent blood from clotting too quickly?
Heparin
Margination
Clinging to capillary walls
What is the function of MAMPs, DAMPs, and PAMPs?
Signals that are sent out so that we can recognize patterns in pattern recognition receptors
Which complement protein binds to antigens?
Cb3
Function of complements
- Lysis
- Opsonization
- Activation of inflammatory response
- Clearance of immune complexes
