Innate Immunity Flashcards
1
Q
Immune System
A
- The immune system fights off foreign material that threatens the body
- Protects against disease
- Consists of two branches:
- Innate: Non-specific
- Adaptive: Highly specific
2
Q
Innate Immune System
A
- Protect humans from most infectious diseases
- Exists at birth and always present
- Natural host resistance
- No memory
- Can be specific for a particular tissue
- Consists of:
- Physical barriers
- Chemical defenses
- Cellular defenses
- Molecular defenses
- Physiological processes
3
Q
Innate Immune System (Part 2)
A
- Infection site and tissue specificity
- Pathogens prefer a specific body site to initiate infection
- Based on nutritional and metabolic needs
- Mechanism of spread
- Aerosols vs blood/bodily fluids
- Clostridium tetani can be ingested or can enter into deep wounds
- Pathogens prefer a specific body site to initiate infection
- Natural host resistance
- Susceptibility to pathogens varies from one species to another
- Anthrax causes fatal blood infection in cattle and cutaneous infection in
humans - HIV can infect human cells but not mice or guinea pigs
- Anthrax causes fatal blood infection in cattle and cutaneous infection in
- Susceptibility to pathogens varies from one species to another
4
Q
What are the physical barriers to infection?
A
- Skin
- Mucous membranes
5
Q
Skin
A
- Prevents invasion by microbes
- Rich in tough protective protein
- Keratin
- Slightly acidic ~pH 5
- High [NaCl]-periodic drying
- Some fungal infections can grow right on the skin’s surface
- Many require broken skin in order to penetrate and cause infection
6
Q
Mucous membranes
A
- Line tracts in the body
- Respiratory tract, digestive tract, reproductive tract, urinary tract
- Mucous produced by goblet cells
- Traps microbes preventing infection
- Contains antimicrobial secretions
7
Q
Types of Mucous membranes
A
- The respiratory tract
- The gastrointestinal tract
- The genitourinary tract
8
Q
The respiratory tract
A
- Contains the mucocilliary escalator
- Mucosal epithelial cells contain cilia
- Serve to filter incoming air
- Sweeping action of cilia allows the removal of mucous and trapped microbes from the lungs
9
Q
The gastrointestinal tract
A
- The stomach
- Small Intestine
- Large Intestine
10
Q
The stomach
A
- Strongly acidic: pH~2
- Contains proteases
- Few microbes are able to survive in this environment
11
Q
Small Intestine
A
- Pancreatic juice buffers acidity of incoming contents from the stomach: pH ~7
- Contains pancreatic enzymes
- Contains bile from the liver
- Very difficult for microbes to maintain cellular integrity in this harsh environment
12
Q
Large Intestine
A
- Contains the normal microbiota
- Normal resident bacteria that live symbiotically inside of the colon
- Use attachment sites to persist
- Consume undigested nutrients
- Competitive exclusion
- Produce antimicrobial compounds
- Microbial antagonism
13
Q
The genitourinary tract
A
- Genital and urinary tracts are separate in females and joint in males
- Urinary tract contains urine
- Includes many toxins that are intolerable by bacteria
- The act of urination physically removes contaminating microbes
- The female reproductive tract contains normal microbiota
- Glycogen secreted by vaginal epithelial cells supplies nutrients for microbial growth
- Lactobacillus acidophilus
- Ferments glucose to lactic acid
- Local pH ~4.5
- Ferments glucose to lactic acid
- Lactobacillus acidophilus
- Glycogen secreted by vaginal epithelial cells supplies nutrients for microbial growth
14
Q
The Lymphatic System
A
- Composed of organs and vessels that allow immune cells to contact foreign
antigenic material- An antigen is foreign material that is able to activate cells of the immune
system
- An antigen is foreign material that is able to activate cells of the immune
- Components of the lymphatic system include:
- Lymphatic vessels
- Lymphoid organs:
- Primary lymphoid organs
- Secondary lymphoid organs
15
Q
Lymphatic vessels
A
- Carry lymph from the tissues to the lymph nodes
- Unidirectional (always away from tissues)
- Lymph is rich in leukocytes (white blood cells)
- Free of erythrocytes (red blood cells)
16
Q
Primary lymphoid organs
A
- Bone marrow
- Leukocytes are produced here
- Thymus gland
- Some leukocytes mature here
17
Q
Secondary lymphoid organs
A
- Lymph nodes
- Spleen
- Mucosa associated lymphatic tissue (MALT)
- **All contain a high concentration of leukocytes
- Incoming lymph is filtered
18
Q
Mucosa Associated Lymphatic Tissue (MALT)
A
- Associated with all mucous membranes
- GALT: Gut Associated Lymphatic Tissue
- Leukocytes present here are constantly phagocytosing material in their surroundings in search of foreign conten
19
Q
Leukocytes-white blood cells (Cellular defenses)
A
- Leukocytes-white blood cells
- Circulate in the blood and the lymphatic system
- Reside in the tissues and the lymph nodes
- Play a role in both innate and adaptive immunity
- Two broad categories:
- Granulocytes
- Agranulocytes
20
Q
Granulocytes
A
- Large, visible granules in the cytoplasm
- Granules are reactive
- Can kill microbes
- Can serve as signaling molecules to recruit and activate other components of the immune system
- 3 types of granulocytes
- Neutrophils
- Eosinophils
- Basophils and Mast Cells
21
Q
Neutrophils
A
- Cytoplasmic granules contain
- Lysozyme
- Defensins
- Circulate in the blood
- Exit the capillaries during
periods of infection
- Exit the capillaries during
- Strongly phagocytic
- Very important cells of the innate immune system
22
Q
Eosinophils
A
- Non-phagocytic cells
- Cytoplasmic granules will stain with acidic dyes
- Work to destroy large parasitic cells
- Protozoa and parasitic worms
- Secrete extra-cellular enzymes and reactive oxygen species
- H2O2, OH., O.
- Can also exit the capillaries into infected tissues
23
Q
Basophils and Mast Cells
A
- Cytoplasmic granules stain with basic dyes
- Not strongly phagocytic
- Basophils circulate in the blood
- Mast cells reside in mucosal tissue
- Degranulate in response to appropriate stimuli
- Release histamine
- Important part of the allergic response
- Causes vasodilation locally
- Causes life threatening vasodilation and bronchiolconstriction when released systemically
- Release histamine
24
Q
Agranulocytes
A
- Contain cytoplasmic granules that are much
smaller and more difficult to view than granulocytes - Include:
- Monocytes
- Lymphocytes
25
Monocytes
1. Macrophages
2. Dendritic Cells (DCs)
26
Macrophages
- Located in the tissues
- Lungs, connective tissue, spleen, liver
- Contain special surface receptors that allow them to recognize many pathogens with one receptor
- Toll-like Receptors (TLRs)
- Recognize things like LPS, peptidoglycan, elements of the fungal cell wall
- Binding of the toll-like receptor to antigen
induces phagocytosis
27
Dendritic Cells (DCs)
- Found in tissues that are often sites of entry for infectious materials
- In the skin they’re called Langerhan’s Cells
- Also found in the mucus membranes of the nose, the lungs and the intestines
- Regularly sample the surroundings and phagocytose antigens
- Phagocytosed antigen is carried to lymphoid organs
- Presented to other cells of the immune system
(T/B lymphocytes)
- Activate the adaptive immune response
28
Lymphocytes
- Leukocytes the are involved in the adaptive immune response
- Circulate through the blood and remain in the lymphoid organs
- B lymphocytes
- T lymphocytes
- Natural Killer Cells (NK cells)
29
B lymphocytes
- Also called B cells or plasma cells
- Antibody producing/secreting cells
- Form the main component of humoral immunity
30
T lymphocytes
- Also called T cells
- Different types
- Form the main component of cell mediated immunity
31
Natural Killer Cells (NK cells)
Destroy abnormal cells in the body (cancer cells, infected cells)
32
Molecular defenses
- Secreted at mucosal sites
- Lysozyme:
- Cuts b-1,4 glycosidic bonds in peptidoglycan
- Defensins:
- Antimicrobial peptides that poke holes in bacterial cell membranes
33
Phagocytosis
- Destroys pathogens that may have never before been encountered in the body
- Involves leukocytes capable of phagocytosis
- Neutrophils and macrophages
- Recognize pathogen associated molecular
patterns (PAMPS):
- Lipopolysaccharide, lipoteichoic acid, flagellin
- PAMPs are recognized by TLRs located on the surface of phagocytic cells
- TLRs are also called pattern recognition receptors (PRRs)
- Interaction of PAMP with a TLR triggers phagocytosis
34
Phagocytosis (Part 2)
- Phagocytes engulf and destroy invading microbes
- Cell membrane invaginates around a foreign particle
- Engulfs it into a phagosome
- Phagosome fuses with a lysosome to form a phagolysosome
- Filled with:
- Lysozyme and defensins
- Proteases (degrade proteins)
- Lipases (degrade phospholipids)
- Nuclease (degrade nucleicacids)
- Oxygen independent killing
35
Phagocytosis (Part 3)
- Oxygen dependent killing:
- Activated phagocytes produce reactive oxygen
compounds:
- H2O2, O2*, OH*, HOCl, NO
- Kill ingested microbes by oxidizing cell components
- Once invaders have been killed:
- Neutrophils perform exocytosis
- Fragments are expelled from the cell
- Macrophages and Dendritic cells become antigen presenting cells
- Fragments of the intruder are presented on
the cell surface to trigger an adaptive immune response
36
Inflammation
- Occurs non-specifically in response to tissue damage, toxins, and infectious material
- Five cardinal signs of inflammation are:
- Redness (erythema), warmth, pain, swelling
(edema) and loss of function
- In response to infection injured tissue and leukocytes release pro-inflammatory
cytokines
- Blood vessels dilate
- Allows more leukocytes to access the area
37
Inflammation (Part 2)
- Vessel walls become more permeable
- Leukocytes can squeeze into tissues
- Extravasation
- Attack invading pathogens
- Temperature increase may slow the growth of pathogens
- Also promotes faster healing of damaged
tissues
- Blood leaking into tissue spaces can clot
- Prevents movement of pathogens
38
Fever
- An increase in body temperature
- Controlled by the hypothalamus of the brain
- It is triggered by toxins, LPS, and chemicals produced by the immune system
- All of these things reset the bodies thermostat
39
Fever Results In
- Muscle contraction-shivering
- Increased temperature-faster metabolism and promoted healing
- Faster phagocytosis
- Slower growth of microbes
- E. coli prefers to grow at 37℃
- Growth slows at 40℃
- Up to a certain temperature fever is a defense against disease
- Fever above 43℃ can cause death
