Ch 16 - Innate Immunity Flashcards
Pathogen-associated Molecular Patterns (PAMPs)
Molecules associated with groups of pathogens that are recognized by cells of the innate immune system
2 branches of the immune system
Innate Immunity
Nonspecific responses present before exposure to an agent (ex. inflammatory response, fever)
2 branches of the immune system
Adaptive Immunity
Develops after exposure to an agent & has memory (ex. humoral response produces antibodies to bind targets, cell-mediated response directly destroys targets)
Overview
Physical Factors
- Skin
- Mucous Membranes
- Normal Flora
Overview
Chemical Factors
- Sebum
- Lysozyme
- Cerumen (earwax)
- Saliva
- Gastric Juices
- Vaginal Secretions
- Urine
- Antimicrobial Peptides
- Iron-binding Proteins
- Complement
- Interferons
Overview
White Blood Cells
- Granulocytes
- Agranulocytes
Thymus
Lymph Node
Thoracic Duct
Spleen
Large Intestine
Small Intestine
Peyer’s Patch
Lymphatic Vessel
Red Bone Marrow
Lymphoid Tissue
Lymphocytes
Skin
Epidermis
Outer portion made of rightly packed epithelial cells containing keratin
Skin
Keratin
A protective protein
Skin
Dermis
Inner portion made of connective tissue
Skin
Skin
Shedding and dryness of skin inhibits microbial growth
Mucous Membranes
Mucous Membranes
Epithelial layer that lines the gastrointestinal, respiratory, and genitourinary tracts
Mucous Membranes
Mucus
Viscous glycoproteins that trap microbes and prevent tracts from drying out
Mucous Membranes
Lacrimal Apparatus
Drains tears & washes eye out
Ciliary Escalator
Transports microbes trapped in mucus out of the lungs
Earwax
Prevents microbes from entering the inner ear
Urine
Cleans the urethra
Peristalsis
Defecation
Vomiting
Diarrhea
Normal Microbiota
Compete with pathogens via microbial antagonism. Produce substances harmful to pathogens, alter conditions that affect pathogen survival
Commensalism
One organism benefits while the other (host) is unharmed
Probiotics
Live microbial cultures administered to exert a beneficial effect
Sebum
Forms a protective film and lowers the pH of skin
Lysozyme
In perspiration, tears, saliva, and urine destroys bacterial cell walls
Gastric Juice
Low pH (1.2-3.0) destroys most bacteria and toxins
Vaginal Secretions
Low pH (3-5) inhibits microbes
Antimicrobial Peptides (AMPs)
Short peptides produced in response to protein and sugar molecules on microbes. Inhibit cell wall synthesis and form pores in plasma membranes. Have a broad spectrum of activity against bacteria, fungi, and viruses
Acute Phase Proteins
Produced in the liver. Limit an essential nutrient to inhibit microbial growth (colonization & spread)
Limiting iron available
Transferrin
Transport/storage protein found in blood and tissue fluids
Limiting iron available
Lactoferrin
Transport/storage protein found in milk, saliva, and mucus
Limiting iron available
Ferritin
Transport/storage protein found in the liver, spleen, and red bone marrow
Limiting iron available
Hemoglobin
Transport/storage protein located in red blood cells
Siderophore Proteins
Produced by bacteria to compete with host iron-binding proteins to scavenge iron
The Complement System
The Complement System
s
Pathway
The Classical Pathway
Requires antibodies
Antibodies bind to antigens, activating C1
C1 splits and activates C2 and C4
C2a and C4b combine and activate C3
C3 functions in cytolysis and opsonization
Pathway
The Alternative Pathway
Does not require antibodies
Factors B, D, & P bind to microbe
C3 combines with factors B, D, P
C3 splits into C3a and C3b, functioning the same as in the classical pathway
Pathway
The Lectin Pathway
Does not require antibodies
Macrophages ingest pathogens releasing cytokines that stimulate lectin production in the liver
MBL binds to mannose activating C2 and C4
C2a and C4b activate C3 which functions the same as in the classical and alternative pathways
Lectin
Lectin Pathway
Mannose-binding Lectin (MBL)
Pathway
Complement Activation
- Cytolysis
- Opsonization
- Inflammation
Complement Activation
Cytolysis
Complement Activation
Membrane Attack Complex (MAC)
Complement Activation
Opsonization
Promotes attachment of a phagocyte to a microbe
Complement Activation
Inflammation
Activated complement proteins bind to mast cells, releasing histamine
Complement Activation
Regulation of Complement
Regulatory proteins readily break down complement proteins, minimizing host cell destruction
Complement Activation
Complement and Disease
Lack of complement proteins causes susceptibility to infections
Complement Activation
Evading the Complement System
Bacterial capsules prevent complement activation
Interferons
Interferons
Antiviral cytokines produced by host cells
Interferons
Type I (IFN-a & IFN-b)
Produced by infected cells cause neighboring host cells to produce antiviral proteins that inhibit viral replication (stop RNA production)
Interferons
Type II (IFN-y)
Causes neutrophils and macrophages to kill bacteria
White Blood Cells
White Blood Cell (WBC) Counts
Measure leukocytes in the blood. High WBC indicate bacterial infections, autoimmune diseases, or side effects of medications
White Blood Cells
Immunity
Ability to ward off disease
White Blood Cells
Susceptibility
Lack of resistance to a disease
Phagocytes
Neutrophils, monocytes, eosinophils
Plasma
Cells and cell fragments suspended in plasma
-Erythrocytes (RBC)
-Leukocytes (WBC)
-Platelets
Created in red bone marrow stem cells via hematopoiesis
Leukocytes
Granulocytes
Leukocytes with granules in their cytoplasm that are visible with light microscope
Phagocytes
Neutrophils
Phagocytic, work in early stages of infection
Phagocytes
Basophils & Mast Cells
Release histamine; work in allergic responses
Phagocytes
Eosinophils
Phagocytic; produce toxic proteins against parasites & helminths
Leukocytes
Agranulocytes
Leukocytes with granules in their cytoplasm that are not visible with a light microscope
Phagocytes
Monocytes
Mature into macrophages in tissues where they are phagocytic
Phagocytes
Dendritic Cells
Found in the skin, mucous membranes, and thymus; phagocytic
Agranulocytes
Lymphocytes
NK cells produce perforin & granzymes to kill infected & cancerous host cells
T cells and B cells play a role in adaptive immunity
Phagocyte Migration & Phagocytosis
Margination
The sticking of phagocytes to blood vessels in response to cytokines at the site of inflammation
Phagocyte Migration & Phagocytosis
Diapedesis
Phagocytes squeeze between endothelial cells
Phagocytes
Phago
(Greek) Meaning Eat
Phagocytes
Cyte
(Greek) Meaning Cell
Phagocytes
Fixed Macrophages
Residents in tissues and organs
Phagocytes
Free (wandering) Macrophages
Roam tissues and gather at sites of infection
Pathogen Recognition
Pathogen-associated Molecular Patterns (PAMPs)
Molecules associated with pathogens are recognized by phagocytes (ex. Peptidoglycan, Flagellin, LPS, Lipopeptides, Viral DNA or RNA)
Pathogen Recognition
Toll-like Receptors (TLRs)
On phagocytes attach to PAMPs
Phagocytosis
Chemotaxis
Chemical signals attract phagocytes to microorganisms
Phagocytosis
Adherence
Attachment of a phagocyte to the surface of the microorganism
Phagocytosis
Ingestion (Opsonization)
Microorganism is coated with serum proteins, making ingestion easier
Phagocytosis
Digestion
Microorganism is digested inside a phagolysosome
Activation of Adaptive Immunity
Activation of Adaptive Immunity
TLRs bound to PAMPs induce the release of cytokines from innate immune cells that regulate the intensity and duration of immune responses
Activation of Adaptive Immunity
Cytokines
Inflammation
The body’s local response to damage.
Functions of Inflammation
- Destroy injurious agent
- Limit injurious agent effects on the body
- Repair & replace tissue damaged by the injurious agent
5 Signs and Symptoms of Inflammation
- Erythema (redness)
- Edema (swelling)
- Heat
- Pain
- Altered Function
Acute Inflammation
The body’s immediate local response to damage
Acute Inflammation
1st
Vasoconstriction for blood loss
Acute Inflammation
2nd
Vasodilation & increased vascular permeability by histamine released from damage cells
Acute Inflammation
3rd
influx of phagocytes that will recognize PAMPs
Fever
Abnormally high body temperature. Higher temperature good for some immune responses. Higher temperatures slow mesophilic bacterial growth.
Hypothalamus is normally set at 37C. Cytokines released in response to LPS cause the hypothalamus to release prostaglandins that reset to a higher temperature. Body constricts the blood vessels, and shivering occurs to raise temperature. After the infection, vasodilation and sweating occurs and the body temperature falls (crisis)