Chapter 8 - Infection and Defects in Mechanisms of Defense Flashcards
Communicability
ability to spread from one individual to others and cause disease
Infectivity
ability of a pathogen to invade and multiply in a host
Infectivity involves a_______, e_______, d_________
-attachment
-escape of phagocytes
-dissemination (spread)
Virulence
severity or harmfulness of a disease or poison
Toxigenicity
ability to produce toxins
What do toxins influence?
a pathogen’s virulence
Portal of Entry
route by which a pathogen infects the host
What are some mechanisms of portal of entry?
-direct contact
-inhalation
-ingestion
-animal or insect bite
Is the DNA in a prokaryote cell enclosed in a nucleus?
no, it only has a nucleoid
Are prokaryotes aerobic or anaerobic?
they can be either depending on the species
Are gram-positive or gram-negative bacteria more dangerous?
gram-negative due to their outer membrane and porin channels which make them more difficult to defeat
Staphylococcus aureus is a common n______ infection
nosocomial
Where are staphylococcus aureus housed as normal microbiota?
nasal passages and skin
S. aureus produces a protein that blocks…
compliment attack
How does S. aureus avoid innate immunity?
producing inhibitors that avoid recognition by the immune system
What enzyme does S. aureus resist when engulfed by a phagocyte? How?
resists Lysozyme by changing the chemistry of their cell walls
S. aureus resists the action of many of what kind of drugs?
antibiotics
Exotoxins are released from ____ the pathogen
inside
Endotoxins are released from ______ the pathogen.
outside, specifically the outer capsule
What are exotoxins?
enzymes that damage host cell plasma membranes or inactivate critical protein synthesis enzymes
What do endotoxins activate? What do they produce?
they activate the immune system and produce fever
Bacteremia and septicemia are a result of the failure of ______ _________
defense mechanisms
Bacteremia
presence of bacteria in the blood
Septicemia
growth of bacteria in the blood
What two systems that start with “C” are activated by endotoxins?
complement and clotting systems
Endotoxins increase capillary permeability which leads to…
large volumes of plasma leaking into surrounding tissue and thus HYPOTENSION
What is the most common cause of pain or distress in humans?
viral disease
Viruses must _____ the host cell to replicate
enter
What is the structure of a virus?
it is neither a eukaryote or prokaryote and is just DNA or RNA surrounded by a capsid or envelope
Viruses are self-limiting meaning…
they resolve spontaneously without treatment or intervention
How are viruses transmitted?
-aerosol
-blood
-sex
-vector (tick, mosquito, etc.)
Viruses have cytopathic effects meaning…
they cause damage to living cells
Viruses inhibit host cell DNA or RNA _______
synthesis
How do viruses kill cells?
release lysosomes into the cell
Viruses can cause the _____ of host cells into multicellular giant cells
fusion
Viruses can cause the alteration of host cell antigen properties causing the immune system to attack…
its own cells
Can viruses cause cancer?
yes, they can transform host cells into cancerous cells
Why do viruses need host cells to replicate?
need to use the host cell resources
What is influenza?
a highly contagious viral infection of the respiratory passages
Influenza has the ability to produce antigenic variation meaning…
ability to change viral antigen spikes yearly
Fungi
are large eukaryotes with thick, rigid cell walls
Why do fungi have the ability to resist penicillin?
penicillin is a fungus itself
Fungi can exist as _____, _____, or both
yeasts or mold
Yeasts are ____cellular
unicellular
Molds are _____cellular
multi
How do yeasts reproduce?
by simple division or budding
How do molds reproduce?
they have branching hyphae and form a mycelium (ie. ringworm)
Mycoses are diseases caused by ______
fungi
What are dermatophytes?
fungi that invade skin, hair, or nails
What are the diseases dermatophytes produce called?
“tineas” ie. tinea capitis (scalp)
Fungal infections adapt to the host environment by having wide t________ variations and requiring low levels of o______-
temperature; oxygen
A low count of what blood cell promotes fungal infections?
white-blood-cells
Which fungus is the most common cause of fungal infections?
Candida albicans, especially in cancer and transplant patients
Candida albicans is housed as normal microbiota in…
skin, GI tract, and the vagina
How might immunocompromised people be affected by Candida albicans?
it can result in a deep infection with high mortality rates
What is the death rate of disseminated (spread) cadidiasis?
30-40%
Parasites are ___cellular protozoa
unicellular
What are helminths?
large worms such as flukes, nematodes, tapeworms
How are parasites spread to humans?
vectors or ingestion of contaminated food or water
How do parasites damage tissue?
by toxins or the inflammatory/immune response
What is the virus that causes Malaria called?
plasmodium vivax
Where does the malaria infection occur?
red blood cells
Malaria results in anemia within __-__ hours
48-72 hours
What causes the symptoms of malaria (fever, chills, vomiting)?
cytokine release (TNF-a and IL-1)
What are antibiotics?
natural products of fungi or bacteria that affect the growth of specific microorganisms
Antimicrobials can be b_______ or b______
bactericidal or bacteriostatic
Bactericidal
agent that kills other microorganisms
Bacteriostatic
agent that inhibits growth of other microorganisms
What two factors are causing a rise in antibiotic resistance?
-lack of compliance with regimen
-overuse
Lack of compliance means…
not using the antibiotic for the prescribed duration
What does lack of compliance result in?
the strongest microbes are left alive to repopulate with resistance to the antibiotic
What does overuse of antibiotics lead to?
destruction of the normal microbiome to open space for more infectious and resistant pathogens
What are vaccines?
biological preparation of weakened or inactivated pathogens
How long does it take the adaptive immune system to respond to a pathogen?
2 weeks
What does a vaccine do?
activates an adaptive response (2 weeks) against a non-viral pathogen
What is the result of a vaccine?
when viral infection occurs, there is no 2 week delay because adaptive immunity is already prepared
Can vaccines be mixtures of different pathogens?
yes ie. DTaP or MMR
Herd immunity requires what % of the population to be immunized?
85%
What is a toxoid?
a chemically altered pathogen toxin injected to allow the body to learn to defeat it (ie. Tetanus toxoid)
Passive immunotherapy involves giving p_______ antibodies to a person
preformed
Passive immunotherapy is becoming more the focus with the rise in antibiotic _______
resistance
What is human immunoglobulin?
antibodies obtained from a pathogen survivor
What causes primary (congenital) immunodeficiency?
genetic defect
What causes secondary (acquired) immunodeficiency?
another illness (ie. cancer)
Most primary immune deficiencies result from how many gene defects?
one
Are primary immune deficiency mutations sporadic or inherited?
sporadic, the mutation occurs before birth
Sporadic Gene Mutation
mutation that is not inherited by parents but can be passed on to the children of the person who acquired the disease via mutation
When do the symptoms of a primary deficiency appear?
early OR late in life
1 in ___ Canadians have a primary immune deficiency but __% of these cases are undiagnosed.
1 in 200; 70%
How are primary immune deficiencies categorized?
based on what aspect of the immune system is defective (ie. B and T lymphocyte or antibody deficient)
Combined Immune Deficiency
group of rare genetic disorders of the immune system (ie. SCID, DiGeorge, Hypogammaglobulinemia)
Severe Combined Immunodeficiency (SCID) results from an underdeveloped ________
thymus
What does the thymus do?
produces T cells
What results from SCID?
absence of T cells (lymphocytes)
DiGeorge syndrome results from a dysfunction of the ________ and ________ gland
thymus and parathyroid gland
What is the result of DiGeorge syndrome?
-inadequate T cell production (thymus)
-plasma calcium management impaired (pt gland)
Hypogammaglobulinemia results from a defect in __ cell maturation or function
B cells
What is the result of Hypogammaglobulinemia?
low levels of circulating antibodies (immunoglobulins) in the blood
Are primary or secondary immune deficiencies more common?
secondary
Why are secondary immune deficiencies not as clinically relevant?
the degree of immune deficiency is usually minor
What are some extreme secondary deficiencies?
AIDS or cancer
How do you evaluate immunity?
complete blood count (CBC) with differential
What is a complete blood count (CBC)?
the total number of RBC, WBC, and platelets in the blood
What is ‘differential’?
the individual numbers of lymphocytes, monocytes, granulocytes
Immunity Evaluation: Quantitative determination of ___________ of immunoglobulins
subpopulations
What does ‘total complement assay’ measure?
the total number of complements (MAC) in blood
Replacement Therapies for Immune Deficiencies: Stem Cell Transplant
taking stem cells from bone marrow or umbilical cord cells to improve immunity
Stem cell transplant results are usually __(temporary/permanent)__
temporary
Replacement Therapies for Immune Deficiencies: Mesenchymal Stem Cell (MSCs) Injection
uses undifferentiated stem cells in bone marrow that eventually undergo differentiation
MSCs injections have strong immunosuppressive properties meaning…
they can stop a variety of immune functions as well
Replacement Therapies for Immune Deficiencies: Gene Therapy
insertion of normal genes into defective genetic material which reconstitutes the immune system
What do some gene therapy recipients develop?
leukemia
What viral disease causes Acquired Immune Deficiency Syndrome (AIDS)?
Human Immunodeficiency Virus (HIV)
What does HIV do?
depletes helper T cells necessary for T and B cell activation
What is the result of HIV?
dysfunctional adaptive immune system that increases susceptibility to disease, AIDS
____sexual activity is the most common transmission route for AIDS
heterosexual (M/f)
Are more women or men infected by AIDS?
more than 50% are women
How do children contract HIV from their mothers?
across placenta or by breastmilk
Why has a HIV vaccine not been developed?
HIV has variable antigen and genetic properties
What is the issue with the antibodies of people with HIV?
they have lots but they aren’t protective, meaning even vaccine antibodies may not function effectively
Epidemiology
branch of medicine that deals with incidence, distribution, and control of disease
What is anti-retroviral therapy (ART) and what is it used for?
a drug containing RNA rather than DNA (retroviral) used to treat HIV
What does ART do?
uses a combination of entrance, reverse transcriptase, integrase, and protease inhibitors to stop HIV from reproducing in cells
Is ART curative of HIV?
no, but it decreases mortality rate
Hypersensitivity is an…
altered immunological response to an antigen that results in disease or damage to the host
3 Types of Hypersensitivity
- allergy
- autoimmunity
- alloimmunity
Allergy
effects of hypersensitivity to environmental antigens (ie. pollen, bee sting)
Exogenous Antigens
environmental antigens found outside human cells
Endogenous Antigens
antigens found within human cells
What is autoimmunity?
a disturbance in immunological tolerance of self-antigens (immune system doesn’t recognize its own antigens)
What are autoimmune diseases?
clinical disorders of autoimmunity
What is alloimmunity?
an immune reaction to the tissue of another individual
When do alloimmune reactions occur?
blood transfusions, transplants, pregnancy
How are hypersensitivity reactions characterized?
by their immune mechanism (Type I, II, III, IV)
What do we mean when saying “hypersensitivity mechanisms are interrelated”?
hypersensitive reactions usually include more than one type of immune mechanism
Immediate Hypersensitivity Reaction
reaction occurs within minutes or hours (ie. Anaphylaxis)
Anaphylaxis
the most rapid and severe immediate reaction that occurs within minutes
Anaphylaxis symptoms
-pruritis: severe itching
-erythema: red patches on skin
-vomiting
-diarrhea
-difficulty breathing
Delayed Hypersensitivity Reaction
reaction occurs after several hours, are at maximal several days later
Type I Hypersensitivity = ___ mediated
IgE (+ products of mast cells - histamine)
What is the most common hypersensitivity reaction?
Type I
Type I occurs against ________ antigens, inducing an allergic reaction
environmental
Step 1: Type I Reaction - Initial Exposure to Allergen
sensitization: IgE binds to mast cell receptors
Step 2: Type I Reaction - Subsequent Exposure to Allergen
hypersensitive reaction: mast cells release cytokines (histamine)
During a Type I reaction which tissues are most commonly affected? Why?
skin, GI tract, and pulmonary tract tissues that have lots of mast cells
Atopic
individuals predisposed to developing allergies when they have parents with allergies
If one parent has allergies, ___% of offspring will
40%
If both parents have allergies, ____% of offspring will
80%
Example of Type I hypersensitivity
Hay fever
Type II (cytotoxic) Hypersensitivity = ______ specific
tissue
What does Type II do?
antibody mediated destruction of healthy host cells
Type II is a reaction against a _______ cell or tissue
specific
Tissue-Specific Antigens
attach only on the plasma membranes of certain cells (ie. platelets)
How many mechanisms of Type II exist?
5 - A, B, C, D, E
Step 1 of Type II Reaction (for all 5 subtypes)
antibody bind to tissue-specific antigens
Type II Mechanism A (hint: compliment)
cell is destroyed by antibodies and compliments (MAC ruptures cell wall)
Type II Mechanism B (hint: eating)
cell is destroyed by phagocytosis via macrophage
Type II Mechanism C (hint: neutrophil)
neutrophils produce toxic products (granules) that damage tissue
Type II Mechanism D (hint: ADCC)
Antibody-Dependent Cell-mediated Cytotoxicity (ADCC) - IgG antibodies bind to antigens and attract NK cells to destroy cell
Type II Mechanism E (hint: block)
mechanism doesn’t destroy the target cell but causes it to malfunction because the antibody binding blocks normal receptor functions
Grave’s Disease is an example of Type II mechanism __
E
Type II example
hemolysis in medication allergies
Type III Hypersensitivity = _______ complex
immune
What is formed in circulation during a type III reaction?
antigen-antibody immune complex
Where is the antigen-antibody immune complex deposited in a type III rxn?
in vessel walls or extravascular tissue
Gluten allergies are an example of a Type ___ reaction
III
Type IV Hypersensitivity = ___ mediated
cell, specifically T cells (not ANTIBODIES)
Mechanism of a Type IV reaction:
reaction activated T cells which activate macrophages to destroy tissues
Type IV reaction examples
graft rejection, poison ivy, metals
