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63 Cards in this Set

  • Front
  • Back
What is the first line of defense from a pathogen?
the mucous/skin
What is the second line of defense from a pathogen?
1) Compliment system
2) Phagocytes
3) Inflammation
What is the compliment system?
a part of the second line of defense, it is a set of proteins that creates a pore in gram negative bacterial membranes
What are the proteins in the compliment system? What are the most important ones, and what do they do?
C1-C9. The most important three are
a) C3a- Activate mast cells, which trigger vasodilation
b)C3b- Opsonin, induces phagocytosis
c) C5a- Chemotactic, attracts immune cells to infection site
c)C5a
What are the two pathways for the compliment system, and how do they differ?
Classical- Activation is done by antibodies, and all C1-C9 proteins are used.
Alternative- Uses microbial cell wall components
What kind of bacteria is unaffected by the compliment system? Why?
Gram-positive, their cell-walls have two layers plus the peptidoglycan and are unaffected by the creation of a pore
What is serum sensitivity?
Testing the sensitivity of a pathogen to the compliment system by exposing pathodens to serum (blood without red blood cells)
What are all immune cells made from?
Bone marrow stem cells
What are the two types of cells made from bone marrow cells?
Myeloid precursor and Lymphoid Precursor
What do myeloid precursors become?
Monocytes and granulocytes. Granulocytes are Neutrophils and Mast Cells
What do Lymphoid precursors become?
T-Cells and B Cells.
How is a T-Cell formed
From a lymphoid precursor, through thymus maturation
How is a B cell formed?
From a Lymphoid, through Bone marrow maturation
What can a Monocyte become?
A macrophage or a dendritic cell
What types of cells are white blood cells made up of?
Monocytes
Granulocytes (Neutrophils and mast cells)
T cells
B cells
What happens to monocytes that become macrophages?
Monocytes are located in the blood, and macrophages are located in the tissue. Also, the monocytes become phagocytic.
What are monocytes attracted to? Why?
Attracted to inflamed tissue, because of C5a's chemotaxis that brings immune cells to the point of infection (inflamed tissue)
What kind of Granulocytes are phagocytic?
Neutrophils
At what stage are Neutrophils found in the inflammation and infection process
In the beginning. They are the main phagocytic cell in early inflammation
What is another name for Neutrophils?
Polymorphonuclear leukocytes
Phagocytosis: what are the steps?
1) Phagocytic cell binds to bacteria
2) Ingestion: Bacteria enters cell, into phagosome
3) Fusion: Phagosome fuses with Lysosome and other granules, creates Phagolysosome which degrades the bacteria
What is a phagosome?
an enclosed vacuum where organisms are put in a phagocytic cell where phagocytosis occurs
What is a phagolysosome?
The fusion of a phagosome and a lysosome
What do Lysosomes contain?
Hydrolytic enzymes.
Generation of Toxic Reactive Oxygen Species: How does it occur? What is its role?
produced by Oxidative bursts by the microphage during infection. produces large amout of toxic oxidative species, which contribute to increased killing of internalized microbes in phagolysosomes, as well as sometimes neighboring cells.
What happens when a macrophage senses endotoxins (LPS), and releases IL-1?
A fever!
What are cytokines? when are they released? What do they do?
Cytokines are signalling molecules of the immune system. They are released when Macrophages sense endotoxins, and cytokines produce Interleukin-1
What is interlukin-1?
A pyrogen, or fever inducing protein, that acts on thermoregulatory part of brain causing body temerature to rise. It is signalled by cytokines released from macrophages that sense endotoxins
What are the steps leading to inflammation?
1) Bacteria enters wound
2) Compliment pathway activated, which creates C3a
3) C3a activated mast cells
4) Mast cells secrete histamine, which mediates vasilodation
5) blood vessels dilate, influx of liquids into tissue, which allows more compliment proteins and immune cells to cross the blood vessel and enter tissue
What is vasodilation?
The enlarging of blood vessels
What is diapedesis? Give an example.
The migration of cells from the blood to the tissue. Ex. in the process of inflammation, mast cells secrete histamines, which cause vasodilatation, which allows immune cells to move from the blood to the tissue.
What is adaptive defense?
The defense that steps in if innate defense cannot eliminate the pathogen. Relies on detection and response to foreign antigens
When is the adaptive defense primed?
during infection, while innate defense is working to eliminate the pathogen
What is an antigen?
A molecule on a microbe recognizable by the host immune system
What are the cells that compose the adaptive defense?
1) B Cells
2) T Cells
3) Antigen-presenting cells (APC's)
What are examples of antigen-presenting cells?
Dendritic cells which present antigens to the T-cell, and macrophages
How does T-cell activation occur?
Step 1) t-cell is presented an antigen by an APC
2) If T-cell is specific for that antigen, it will be activated
Once a T-cell is activated, what happens?
the T-Cell produces Interleukin-2 (IL-2) , which induces multiplication/differentiation of cell into Effector T-cells and memory T-cells
What are the two types of T-cells that IL-2 induces the differentiation of regular T-cells into?
Effector cells: do the job
Memory cells: save it for next time!
What are the two types of T-cells? what do they do?
T-helper cells: activate B cells and microphages
Cytotoxic T cells: Kill host cells that display foreign antigen on surface
What are molecules that present antigens called?
Major histocompatibility complexes (MHC's)
What are the two types of Major Histo Compatibility Complexes?
MHC-1:
-Expressed by all organisms
-present antigen coming form inside of cells
-recognized by cytotoxic T-cells

MHC-2:
-Expressed only on APC's (Microphages and dendritic cells)
- present antigens processed in the phagolysosome ( already digested)
- Recognized by Helper T-cells
How are B-cells activated?
Helper T-Cells
What do B-cells do?
produce antibodies
how is an antigen on the B-cell presented? Who recognizes it?
Presented on MHC-2, recognized by a Helper T cell
What releases B-cell growth factor and B-cell differentiation factor?
Helper T cells
What is B-Cell growth factor (BCGF)?
a factor released by Helper T-cells that induces multiplication and production of plasma cells (which produce lots of antibodies) in B-cells
what is B-cell differentiation factor (BCDF)?
Makes B-cells into memory B-cells.
How is a B-cell made into a memory B-Cell?
BCDF
What does a memory B-Cell do?
Memory B-cell does not make antibodies to fight the infection right away, but instead waits for the next infection by that pathogen and then produces lots of antibodies
What are antibodies made of?
Immunoglobins, which are groups of relatied proteins.
What are immunoglobins?
groups of related proteins in antibodies
What are the two sections of an antibody? describe them
The variable binding site: Every B-cell makes antigen w/ different binding site, but they all work because variability in their range of binding.
Constant region- Binds to receptor on microphages and activates compliment system
What are the three main types of antibodies?
IgG:
-Major Circulating antibody
-found in lymph, blood, and extra cellular fluid
IgM:
-first antibody to appear
-in blood and lymph only
-Causes aggregation of antigens
- Pretty big

IgA:
-secretory antibody
- found in extra-cell fluid and mucus
-in mucus, stops pathogen from going any further
What are the functions of an antibody?
1) To promote phagocytosis
- achieves this by acting like an opsonin (C3b)
- attaches to surface of antigen on microbe
- Fc (constant) region of antibody binds to FcR on macrophage to make sure microbe gets eaten
2) to bind to surface on microbe cells
3) To bind to toxins
- prevent toxin from entering host cells
-antibody can bind to adhesins, blocking adhesins from binding to host cells, tehrefore stopping bacterial colonization
4) Activation of compliment
- Classical pathway
- leads to production of more C3a,C3b, C5a
What is an opsonin? what is an example
a molecule that targets an antigen for an immune response. Ex. C3b, antibodies
How are macrophages activated?
by Helper T-cells
What is an angry killer cell? How is it caused, and what are its properties?
a macrophage that has been activated by a helper Tcell. Helper T-cell induces differentiation of macrophages--> angry killer cells

- higher phagocytic activity
- more hydrolytic enzymes
-increased oxidative burst capacity
How does a Cytotoxic cell know what to kill? How does it kill?
It identifies foreign antigens presented on an MHC-1, and then releases granules of granzymes and perforins that kill the cell.
What is the role of a memory cell?
Ensures that the immune response following a second exposure will be faster and stronger
What is natural immunity a result of?
Probably the lack of key receptors for the pathogen ( same thing for toxins)
What is natural immunity?
Immunity that we have without having built it up.
What are the types of acquired immunity?
1)Active immunity:
-caused by memory cells
- naturally: following infection (i.e. chicken pox)
- artificially: vaccination (i.e. using love/attenuated/dead agents of adhesins, toxoids or capsular polysaccharides)

2) passive immunity:
-acquisition of pre-formed antibodies
-Naturally: placental transfer or colostrum (first mL's of breast milk chalk full of antibodies)
-Artificallly: Injection of serum from immune animal into human to gain their antibodies