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Who are the most succeptible to infections?
- Younger children 1-4
- Older adults over 50
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What is species resistance?
Correct chemical receptors are not present on human cells for pathogens that affect other species. Also the conditions may be incompatible with those needed for pathogen's survival
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What are human pathogenic agents?
- bacteria
- viruses
- fungi
- parasites
- pollution
- toxins
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Why does the immune system not destroy our body cells?
because when we are young the body develops a tolerance and learns what not to attack and what to attack
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What are the 4 classes of pathogens that the immune system protects against?
- 1. Extra cellular bacteria, parasites, fungi
- 2. intracellular bacteria, parasites
- 3. viruses (intracellular)
- 4. Parasitic worms (extracellular)
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What are some examples and diseases caused by extracellular bacteria, parasites, and fungi?
- examples: streptococcus pneumoniae, clostridium tetani, trypanosoma brucei, pneumocystis carinii
- Diseases: pneumonia, tetanus, sleeping sickness, pneumocystis pneumonia
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What are some examples and diseases of intracellular bacteria and parasites?
- Mycobacterium leprae (leprosy), Leishmania donovani (leishmaniasis)
- Plasmodium falciparum (malaria)
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What are some examples of diseases caused by viruses?
- Variola (smallpox)
- Influenza (flu)
- Varicella (chickenpox)
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What are diseases caused by parasitic worms?
- Ascaris (ascariasis)
- Shistosoma (Shistosomiasis)
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What are the 2 general mechanisms of the immune system?
- 1. Innate immunity (nonspecific mechanisms)
- 2. Adaptive Immunity (specific mechanisms)
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What are some of the characteristics of the response of Innate immunity?
- 1. rapid response (hours)
- 2. fixed (always there and protects against all different kinds)
- 3. limited number of specificities
- 4. constant during response
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What are examples of innate immunity?
- Skin (keratin protects)
- Mucous membranes
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What is an example of adaptive immunity?
Antibodies
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What are some characteristics of the adaptive immune response?
- 1. slow response (days to weeks)
- 2. variable (immunity increases with number of exposures) - booster shots
- 3. numerous highly selective specificities
- 4. improve during response (memory)
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What are the categories of Innate Immunity?
- 1. first line defenses
- 2. phagocytosis
- 3. inflammation
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What is the definition of the body's first line of defense?
Structures, chemicals, and processes that work to prevent pathogens from entering the body (skin and mucous membranes).
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How does the epidermis protect from pathogens?
Multiple layers of tightly packed cells defer most pathogens from penetration. Shedding of dead skin cells removes microorganisms. Epidermal dendritic cells phagocytize pathogens.
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How does the dermis protect against pathogens?
Collagen fibers help skin resist abrasions that could introduce microorganisms.
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What are some other defenses of the skin?
Chemicals that defend against pathogens. Perspiration secreted by sweat glands has salt, which inhibits the growth of pathogens. Antimicrobial peptides act against microorganisms. Lyzsozyme destroys cell wall of Gram (+) bacteria. Sebum secreted by glands helps keep skin pliable and less likely to break or tear and loweres skin pH to a level inhibitory to many bacteria.
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What is the rule of mucous membranes in innate immunity?
Epithelial cells are tightly packed to preven the entry of pathogens. Continual shedding of cells carries away microorganisms.
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What is the role of the lacrimal apparatus in innate immunity?
produces and drains tears, blinking spreads tears and washes surface of the eye. tears contain lysozymes.
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What is the role of normal microbiota in innnate immunity?
they compete with potential pathogens, they consume the nutrients so that there aren't any left for pathogens, they create an unfavorable environment, they stimulate the body's second line of defense, they promote overall health by providing vitamins
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What is microbial antagonism?
Normal microbiota are competing with potential pathogens
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How do antimicrobial peptides act?
- they are present in the skin, mucous membranes, and neutrophils
- -induce holes in bacterial membranes
- -intracellular killing
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When does the body's second line of defense activate?
when pathogens penetrate the skin or mucous membranes
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What is the body's second line of defense?
- 1. Phagocytic cells (blood and tissues)
- 2. Nonspecific chemical defenses against pathogens
- -complement proteins (serum)
- -antimicrobial peptides (all body secretions)
- -interferons (3 types)
- 3. Inflammation (fever)
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What are Interferons?
natural antiviral mechanisms that every cell in our body contains
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What is plasma?
mostly water containing electrolytes, dissolved gases, nutrients, and proteins
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What is serum?
the fluid remaining when clotting factors are removed. it includes iron-binding compounds, complement proteins, and antibodies
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What are formed elements and what are the 3 types?
- Cells and cell fragments.
- 1. erythrocytes
- 2. platelets
- 3. leukocytes (divided into granulocytes and agranulocytes)
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What is hematopoiesis?
the formation and development of cells of the blood
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What are the 3 types of Granulocytes and how do they stain?
- –Basophils – stain blue with basic dye methylene blue
- –Eosinophils – stain red/orange with acidic dye eosin
- –Neutrophils – stain lilac with mix of acidic and basic dyes
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How do neutrophils and eosinophils work?
- –Phagocytize pathogens
- –Capable of diapedesis (Chemotaxis)
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What are complement proteins?
proteins that are activated in the blood when there are pathogens present. they are located the serum.
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What is the smallest leukocyte?
Lymphocytes
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What stem cell forms into lymphocytes?
Lymphoid
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What stem cell forms into erythrocytes?
Erythroid
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What stem cell gives rise to platelets, basophils, neutrophils, eosinophils, and monocytes?
Myeloid stem cell
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What signals the stem cell to become a specific cell?
cytokines
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How do phagocytes move?
chemotaxis
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What is diapedesis?
movement along the surface of the tissue
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Which leukocyte is involved in adaptive immunity?
Lymphocytes
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Which leukocyte leaves the blood and matures into a macrophage?
monocytes
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What does increased eosinophils indicate?
allergies or parasitic worm infection
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what does increased leukocytes and neutrophils indicate?
bacterial infection
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what does increased lymphocytes indicate?
viral infections
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what is phagocytosis?
engulfment of pathogens
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What are the six stages of phagocytosis?
- -chemotaxis
- -adherence
- -ingestion (in phagosome)
- -fusion with lysosome
- -killing
- -elimination
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What happens in the stage of chemotaxis?
signals are sent out to draw macrophages to area
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What happens in the stage of adherence?
the phagocytic cell binds to the pathogen (if the pathogen has slime it is harder to bind to)
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What happens in the last 3 stages of phagocytosis?
The phagosome ingests the pathogen and mixes the pathogen with enzymes that break down the pathogen and kill it.
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What occurs if the pathogen has a slime capsule that makes it difficult to grab?
Opsonization-there are proteins in the serum (complement proteins) or antibodies that provide certain tags (opsonins) on the pathogen for the phagocytic cell to grab
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What stimulates the complement components to be activated?
the surface of the microbe
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What is the definition of an opsonin?
a molecule that promotes phagocytosis by binding to the surface of the microbe and providing tags for phagocytic cells to be able to grab the pathogen
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What cells are involved in nonphagocytic killing?
lymphocytes and eosinophils
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How do eosinophils kill pathogens?
they attack parasitic helminths (worms) by attaching to their surface and secrete toxins that weaken or kill it
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How do natural killer lymphocytes kill?
- they secrete toxins onto the surface of virally infected cells and tumors.
- they can differentiate normal body cells because they have membrane proteins similar to the NK cells
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What are toll-like receptors?
proteins inside of a phagocytic cell membrane that recognize foreign material on the surface of pathogens called PAMPS
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What does PAMP's stand for?
pathogen-associated molecular patterns (in bacteria but not in human cells)
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What is apoptosis?
sending a signal to a cell to kill a pathogen
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What are interferons?
protein molecules released by host cells to nonspecifically inhibit the spread of viral infections
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What are alpha interferons released from?
leukocytes, epithelium
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what are beta interferons released by?
fibroblasts (connective tissue cells)
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How does an interferon work?
when a cell is infected by a virus, interferons are released by that cell and attach to neighboring cells to stop RNA synthesis and release enzymes that break down viral RNA
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What is the pathway that activates the complement by antibody molecules coating the microbes?
Classical Pathway
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What is the pathway that activates the complement with surface components of the microbes?
Alternate pathway
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Which pathway needs immunoglobulins?
classical
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which pathway is faster?
alternate
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Which product of C3 is an opsonin for neutrophils and macrophages?
C3b
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What are C3a and C5a?
anaphylatoxins (cause smooth muscle contraction, histamine release, and vasodilation)
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Which product of C5 is a chemotactic agent for neutrophils and macrophages?
C5a
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Which complement components are known as the "membrane attack complex" and induce holes in the cytoplasmic membrane of pathogens?
C5-9
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Why can the human body's cells withstand the complement cascade?
our cells have inhibitors that can withstand the complement cascade
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What is inflammation?
nonspecific response to tissue damage from various causes characterized by redness, heat, swelling, pain, and loss of function
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What are the two types of inflammation?
acute and chronic
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what are the two main events of inflammation?
- vascular events
- cellular events
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What induces vascular events?
- histamine
- anaphylotoxins (C3a and C5a)
- prostaglandins and leukotrienes (produced by damaged cells)
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What are cellular events characterized by?
migration of phagocytes to the site of injury
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What are some chemotactic factors that cause migration of phagocytes during cellular events?
- C5a
- Interleukin (IL-8) released by macrophages (form of cytokines)
- C3b opsonises pathogens
- Antibody (IgG) is also an opsonin
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What causes a fever?
pyrogens triggering the hypothalamus
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what are some types of pyrogens (fever-producing mechanisms)?
- -bacterial toxins
- -cytoplasmic contents of bacteria released by lysis
- -antibody-antigen complexes (these signal for the production of interleukin-I (IL-1) by macrophages
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What are the five attributes of adaptive immunity?
- specificity
- inducibility
- clonality
- unresponsiveness to self (tolerance)
- memory
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where do B cells mature?
bone marrow
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where do T cells mature?
thymus
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What are the two types of adaptive immune responses?
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What does humoral immunity mean?
B cells produce antibodies
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What does cell-mediated immunity mean?
T cells directly killing pathogens
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What do T helper cells do?
release cytokines to generate a response in other cells, including B cells
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What is lymph?
- –Liquid with similar composition to blood plasma
- –Arises from fluid leaked from blood vessels into surrounding tissues
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How does lymph circulate?
- body movement
- one way valves prevent backflow
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What are the primary lymphoid organs (where cells mature)?
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What are the secondary lymphoid organs (where matured cells reside and function)?
- lymph nodes
- spleen
- tonsils
- mucosa associated lymphatic tissue (MALT)
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What is an antigen?
anything that the body recognizes as foreign and attacks
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what are epitopes?
regions on the antigen that cause a reaction in the T cells. They are specific to certain epitopes.
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what are exogenous antigens?
- antigens that have entered the body from the outside
- Example: inhalation, ingestion, or injection
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What are endogenous antigens?
antigens that have been generated within previously normal cells as a result of normal cell metabolism, or because of viral or intracellular bacterial infection
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What are autoantigens?
normal cell antigens
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Where are B cells usually found?
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How many B cell receptors for a specific antigen does a single b cell generate?
One. they have multiple receptors, but the receptors are specific to a single epitope on an antigen
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•Activation of complement and inflammation
- •Neutralization (can't bind)
- •Opsonization (tags for phagocytes to grab)
- •Agglutination
- •Killing by oxidation
- Antibody-dependent cellular cytotoxicity (ADCC
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What are the five classes of antibodies?
- IgM-first antibody produced (pentameric) comes in a chain of five
- IgG-(serum) most common and longest-lasting antibody
- IgA-associated with body secretions (dimeric) -only one that survives in secretions
- IgE-involved in response to parasitic infections and allergies
- IgD-exact function is not known
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What is the only Antibody that can cross the placenta?
IgG (because it is the smallest)
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What is a T cell called when it has not encountered any antigens?
naive T cell
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What are the differences between T cell receptors and B cell receptors?
- B cells have Y shaped receptors, T cell receptors have 2 chains side by side
- B cells bind to antigens directly, T cells do not. They need an antigen presenting cell to present the antigen to them. Then the T cell binds to MHC2 in order to recognize the antigen
- When a B cell recognizes an antigen, it begins to secrete its receptor. T cell receptors cannot get secreted.
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