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LSCI 230: Microbiology > Host Defenses > Flashcards

Host Defenses Flashcards

1
Q

Cells of the immune system

A
  • Monocytes
  • Granulocytes
  • Lymphocytes
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2
Q

Monocytes

A
  • Circulate In blood stream
  • Attracted to inflamed tissues
  • Phagocytic
  • Differentiate into macrophages & dendritic cells
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3
Q

Granulocytes

A
  • Cytoplams contains granules

Includes:
* eosinophils
* basophils
* neutrophils (phagocytic)
* mast cells (induce inflammation)

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4
Q

Lmphocytes

A
  • T cells: helper, cytotoxic
  • B cells: antibodies
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5
Q

Innate defenses

A
  • Properties of the normal host
  • Non specific
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6
Q

Innate defenses of skin and mucous membrane

A

Skin:
* Thick layer of dead cells

Normal microbiome
* competes for attachment sites and nutrients
* secretes bacteriocin

Antimicrobial substances
* fatty acids
* Lysosymes
* antimicrobial peptides (AMPs)
* Antibodies

Mucous membrane
* Secretes mucous that traps bacteria

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7
Q

Innate defenses of the airways

A
  • Mucous membrane that traps bacteria
  • Ciliated cells remove mucus and trapped bacteria
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8
Q

Innate defenses of tissues and internal fluids

A
  • Complement system
  • Phagocytosis
  • Inflammation
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9
Q

Complement system

A
  • Set of blood proteins
  • Activation results in the formation membrane attach complex (MAC)
  • Causes cell lysis of some Gram-negatives
  • No effect on Gram positives
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10
Q

Complement system activation pathways

A
  • Classical: Antibodies
  • Alternative: Microbial cell wall components
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11
Q

Serum sensitivity

A

Test sensitivity to complement by exposing pathogens to serum

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12
Q

Phagocytosis: Steps

A
  1. Attachement of organism to the membrane of the phagocyte
  2. Ingestion (organism becomes enclosed in a phagosome
  3. Granules containing hydrolytic enwymes fuse zith the phagosome forming the phagolysosome
  4. Oxidative burst (production of ROS)
  5. Killing and digestion of the microorganism
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13
Q

Phagocytes

A
  • Neutrophils
  • Macrophages
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14
Q

Inflammation: Signs

A
  • Redness
  • Heat
  • Swelling
  • Pain
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15
Q

Inflammation: Functions

A
  • Recruitment of immune cells to thje site of infection
  • Increased concentration of molecules
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16
Q

Interleukin-1: Functions

A
  • Increases movement of liquid from blood to tisses and causes inflammation
  • Increases the concentration of immune cells at infection sites
  • Increases the spacing between tissue cells to allow immune cells to enter tissues
  • Activates phagocytes
  • Acts on the thermoregulatory center of the brain and causes fever to limit the growth of pathogens
17
Q

Fever

A
  1. macrophages sense the presence of endotoxins
  2. Production of Il-1
  3. Il-1 acts causes body temp to increas
  4. High T reduces growth of some pathogens
  5. Il-1 activates phagocytes and other cells of the immune system
  6. Causes inflammation
18
Q

Adaptive defenses

A
  • Induced by the infection
  • Rely on the detection and response to foreing antigens
  • Specific to pathogens
19
Q

Cells of the adaptive immune system

A
  • T cells
  • B cells
  • Antigen-presenting cells (APCs)
20
Q

Antigen-presenting cells

A

Macrophages and dendritic cells

21
Q

Major histocompatibility complex (MHC)

A
  • Antigen present molecular complex

MHC I:
* Antigens from inside the cell
* Present on all cells
* Recognised by cytotoxic T cells

MHC II:
* Antigens processed in phagolysosomes
* Present on APCs and B cells
* Recognised by T helper cells

22
Q

T cells types

A

T helper cells:
* Activate B cells and macrophages carrying the specific foreing antigens
* Useful against bacterial pathogens

Cytotoxic T cells:
* Rekease perforins/granzymes that kill host cells carrying the foreign antigen
* useful against infection by viruses/intracellular pathogens

23
Q

Interleukin-2

A

Produced by activated T cells
* Induces multiplication & differentiation into effector T cells and memory T cells

24
Q

Activated macrophages

A
  • increased phagocytic activity
  • produce much higher levels of
    hydrolytic enzymes
25
Q

B cells

A

Produce antibodies

26
Q

Activation of B cells

A
  • The B cell displays its antibody on its surface
  • Pick up the foreign antigen it recognizes
  • Antigen is processed and displayed on its surface by MHC II.
  • A T cell specific for the antigen recognizes this complex and produces Il-4
  • IL-4 activates the B cells which multiplies and differentiates into plasma cells and B memory
    cells
27
Q

Plasma cell

A
  • Activated B cell
  • Produces antibodies
28
Q

Interleukin-4

A
  • Produced by helper T cells
  • Activates B cells
29
Q

Antibodies

A
  • Group of related proteins - immunoglobulins
  • Highly variable antigen binding site (Fab)
  • Constant region (FC) binds to receptor on macrophages
30
Q

Function of antibodies

A
  • Activates complement
  • function as opsonins which increase phagocytosis efficiency
  • Bind to toxins which prevents binding of toxin to host cells
  • Bind to adhesins which prevents adhesion of microorganism to host cells
31
Q

Memory cells

A

Ensure that the immune response, following a second exposure to the same antigen, is faster and stronger

32
Q

Aquired active immunity

A

Involves the production of memory cells in response to antigenic stimulus
* Natural: following infection
* Artificial: vaccination

33
Q

Aquired passive immunity

A

Involves the acquisition of preformed antibodies
* Natural: placental transfer or colostrum
* Artificial: serum from an immune animal

34
Q

Natural immunity

A

Explained in part by the incompatibility of the virulence factor with the genetics of a species

LSCI 230: Microbiology (14 decks)

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