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MBIO 1010 > Innate Immunity > Flashcards

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:
      1. Innate: Non-specific
      2. Adaptive: Highly specific
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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
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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
  • 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
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4
Q

What are the physical barriers to infection?

A
  1. Skin
  2. Mucous membranes
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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
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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
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7
Q

Types of Mucous membranes

A
  • The respiratory tract
  • The gastrointestinal tract
  • The genitourinary tract
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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
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9
Q

The gastrointestinal tract

A
  • The stomach
  • Small Intestine
  • Large Intestine
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10
Q

The stomach

A
  • Strongly acidic: pH~2
  • Contains proteases
  • Few microbes are able to survive in this environment
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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
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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
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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
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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
  • Components of the lymphatic system include:
    • Lymphatic vessels
    • Lymphoid organs:
      • Primary lymphoid organs
      • Secondary lymphoid organs
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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)
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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:
    1. Granulocytes
    2. 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
  • 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
24
Q

Agranulocytes

A
  • Contain cytoplasmic granules that are much
    smaller and more difficult to view than granulocytes
  • Include:
    • Monocytes
    • Lymphocytes
25
Q

Monocytes

A
  1. Macrophages
  2. Dendritic Cells (DCs)
26
Q

Macrophages

A
  • 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
Q

Dendritic Cells (DCs)

A
  • 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
Q

Lymphocytes

A
  • 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
Q

B lymphocytes

A
  • Also called B cells or plasma cells
  • Antibody producing/secreting cells
  • Form the main component of humoral immunity
30
Q

T lymphocytes

A
  • Also called T cells
  • Different types
  • Form the main component of cell mediated immunity
31
Q

Natural Killer Cells (NK cells)

A

Destroy abnormal cells in the body (cancer cells, infected cells)

32
Q

Molecular defenses

A
  • Secreted at mucosal sites
    • Lysozyme:
      • Cuts b-1,4 glycosidic bonds in peptidoglycan
    • Defensins:
      • Antimicrobial peptides that poke holes in bacterial cell membranes
33
Q

Phagocytosis

A
  • 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
Q

Phagocytosis (Part 2)

A
  • 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
Q

Phagocytosis (Part 3)

A
  • 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
Q

Inflammation

A
  • 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
Q

Inflammation (Part 2)

A
  • 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
Q

Fever

A
  • 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
Q

Fever Results In

A
  • 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

MBIO 1010 (13 decks)

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