are disease-producing agents that include infectious organisms, toxic chemical, radiation
What is non-specific resistance?
defends the body against invasion by a wide range of pathogens
Why does the human body harbor so many bacteria?
because homeostasis provides an ideal temperature, enough moisture, suitable pH, and plentiful nutrients for microbial life
Why is the skin a bad enviornment for bacteria?
the skin is typically too dry and nutrient-poor for microbes to survive
Epidermal cells and keratin provide mechanical barrier against microbes
What does the skin secrete that makes it a bad enviornment?
Antimicrobial chemicals and lactic acid come from sweat and from coating over skin
sebaceous glands secrete oily sebum to form a protective film over the skin
How do the mucus membranes defend against pathogens?
line body cavities open to exterior and secrete mucus to trap microbes that try to enter them
How does areolar connective tissue prevent microbes from entering the body?
contains hyaluronic acid, which give it thick, sticky consistency which makes it difficult for microbes to penetrate the skin
How does the lacrimal apparatus defend against microbials?
secretes tears to keep microbes from infecting the eyeballs
How does the saliva defend against microbials?
dilutes the concentration of microorganisms and washes them from the teeth and mouth
How do sweat glands defend against microbials?
produce perspiration to flush microorganisms from the skin
How does urine defend against microbials?
prevents microbial growth in the urinary system by constantly flushing urethra
How do acidic secretions from gastric tract and vaginal walls defend against microbials?
retard bacterial growth in the intestinal tract and female reproductive tract, respectively.
What do mucus, saliva, perspiration, and tears contains?
contain lysozyme, which dissolves bacterial walls
What do phagocytes attack?
Organisms that get past the skin and mucous membranes
How do phagocytes adhere to pathogens?
by recognizing its carbohydrate "signature"
How do neutrophils kill bacteria?
What is a "killing zone" of neutrophils?
a neutrophil releases enzymes to form a “killing zone” around itself, which kills many more bacteria than by phagocytosis
What does the "killing zone" contain?
contains hydrogen peroxide and hypochlorite to kill bacteria and neutrophil, which may contribute to development of rheumatoid arthritis
What are a natural killer cells (NK)?
are large lymphocytes produced in red bone marrow, which can kill wide variety of bacteria and host cells that have become cancerous or gotten infected by with viruses
What happens when NK cells encounter a microbe?
it secretes perforins to rupture membrane and destroy target cell
Where are NK cells found?
are found in blood, spleen, lymph nodes, red bone marrow
What do macrophages develop from?
develop from monocytes and become scavenger cells
What are wandering macrophages?
they leave the blood to seek out pathogens
What are fixed macrophages?
they stand guard in certain tissues and/or organs (skin, liver, lungs, spleen, lymph nodes) and phagocytize pathogens that come to them
What is the function of antimicrobial proteins?
provide a second line of defense against bacteria and viruses that penetrate the skin and mucous membranes
What are interferons?
are proteins produced and released by cells that get infected with viruses
What are the functions of interferons?
they stimulate uninfected neighbor cells to manufacture antiviral proteins that can "interfere with" or inhibit viral replication
they also enhance phagocytosis and activate natural killer cells
What is the complement system?
is a group of 30 or more proteins synthesized by the liver that circulate in the blood plasma in an inactive form
What happens when a pathogen activates the complement system?
splits a protein into fragments that can destroy the pathogen by inflammation, immune clearance, phagocytosis, cytolysis
What is the classiccal pathways?
requires activation of antibodies, which makes it part of immune response
What is the alternative pathways?
Active complement fragments can bind to viruses, bacteria, yeast
What is the lectin pathway?
binds plasma proteins to particular carbohydrates to initiate a reaction cascade
What is inflammation?
is a local response to tissue damage that is designed to limit the spread of a pathogen, to remove debris associated with damaged tissue, and to initiate tissue repair
What are the characteristics of inflammation?
Where does inflammation occur?
can happen anywhere in the body, but is most common in the skin
What mediates inflammation?
mediated by small cytokine proteins that alter the physiology or the behavior of the recipient cell
What produces the redness and heat of inflammation?
Local vasodilation increases blood flow to the damaged tissue causing hyperemia
What increases the permeability of blood vessels and promotes filtration of fluid into the interstitial spaces?
mast cells release histamines; and other cells release kinins, prostaglandins, and leukotrines are released
What produces the pain sensations of inflammation?
Swelling (edema) presses on nerve ending, which combines with bacterial toxins and prostaglandins and kinins
What increases the white blood cell count during inflammation?
Soon after inflammation begins, the damaged tissue is flooded with leukocytes
How is the location of the inflammation signaled?
neutrophils cling to the inner walls of the capillaries (margination)
What does diapedisis allow?
allows leukocytes to change shape and “crawl” through the capillary walls to enter interstitial fluid
What is the role of fribrinogen?
filters into the fluid around the damaged tissue and forms a clot, which sequesters bacteria and other microbes
What is the role of heprin?
prevents blood from clotting in vicinity of injury, so pathogens get trapped in fluid-filled clot
How are neutrophils guided to the inflammation site?
neutrophils are attracted by chemicals that guide them to the site of injury or infection (chemotaxis) and they begin to phagocytize and destroy the bacteria
What happens when neutrophils secrete cytokines?
neutrophils recruit monocytes and more neutrophils by secreting cytokines
What do monocytes do 8-12 hours after injury?
monocytes arrive within 8 to 12 hours following the injury and become wandering macrophages that engulf any remaining bacteria, damaged host cells, worn-out neutrophils, and other debris
What does the pus surround in an abscess?
Dead and dying phagocytes, cellular debris, and living and dead pathogens get surrounded by a thick yellowish pus which accumulates in an abscess
What normally happens to pus?
Pus is usually absorbed from infection site, but if it cannot drain from inflamed region blister may form and require surgical drainage
What is a fever?
is an abnormal elevation of body temperature that results from trauma or infection
Why is a fever a good response?
promotes interferon activity
elevates metabolic rate
inhibits reproduction of bacteria and viruses
accelerates tissue repair
What do fever-producing agents do?
Neutrophils and macrophages secrete fever-producing agents that raise the hypothalamic set-point for body temperature
What does a rising set-point produce?
produces shivering and vasoconstriction to reduce heat loss
What happens to the body temperature while the pathogen is still present?
body temperature oscillates around the new set-point as long as the pathogen is present
What happens to the fever once the pathogen is defeated?
when the pathogen is finally defeated, secretion of fever-producing agents halts and the hypothalamic set-point returns to normal and sweating occur
What can happen to a child after a severe infection?
In children younger than 15, some viral infections may be followed by Reye syndrome
What can Reye syndrome cause?
Brain swelling produces nausea, vomiting, seizures, coma
What can trigger Reye syndrome?
Can be triggered by aspiring, so parent should not give aspirin to children with chickenpox or flu-like symptoms
What does the immune system consist of?
consists of cells and tissues that defend the body against specific bacteria, toxins, viruses, foreign tissues
What does specificity allow the immune system to do?
enables the immune system to identify particular pathogens and to distinguish between self molecules and non-self molecules
How does the immune system respond to subsequent invasions?
the immune system has a memory for encounters with previously identified antigens, which allows it to aggressively respond to subsequent invasions by these pathogens
What is cellular immunity (cell-mediated)?
uses lymphocytes to directly attack and destroy foreign cells or host cells that are infected with bacteria or viruses or yeasts or parasitic worms, or cancer cells or foreign cells as a result of a transplant
What is humoral immunity (antibody-mediated)?
uses antibodies to “label” pathogens for destruction by other mechanisms.
What is naturally aquired active immunity?
occurs when antibodies or T cells are produced in response to a particular pathogen.
What is naturally acquired passive immunity?
is a temporary immunity from the natural transfer of antibodies from an immunized donor to a non-immunized recipient
What is artificially aquired acive immunity?
results from a vaccination
Vaccine contains dead or attenuated pathogens that stimulate body to produce antibodies or T cells
What is artificially aquired passive immunity?
is a temporary immunity from an injection of serum that contains antibodies that were produced outside of the body (horse serum for treatment of snakebite)
What is an antigen?
is an “antibody generating” molecule that shows immunogenicity and reactivity
What type of proteins are antigens?
Most antigens are large, complex proteins that are unique to each individual
What is immunogenicity?
is the ability to provoke an immune response
What is reactivity?
is the ability to interact with specific antibodies or cells
What could an antigen be?
may be an entire microbe, or parts of a microbe or bacterial cell walls, or bacterial toxins, or incompatible blood cells, or even pollen or egg whites
What is the only thing that can trigger an immune response?
Only an epitope can trigger an immune response
What can antigens do with their multiple epitopes?
most antigens have several epitopes that either induce the production of specific antibodies or activate specific T cells
What are haptens?
are small molecules that attach to larger molecules and create unique complexes that the immune system can recognize as foreign
Poison ivy, penicillin
How are T lymphocytes formed?
are “born” in red bone marrow from pluripotent stem cells.
How are the T lymphocytes stimulated?
they travel to the thymus gland where thymic hormones stimulate them to develop surface antigen receptors and become immunocompetent
How are B lymphocytes formed?
Other fetal stem cells remain in the bone marrow and differentiate into B lymphocytes
What must happen in order for a immune response to occur?
The presence of a foreign antigen must be detected
Where are exogenous antigens found?
are found in the extracellular fluid outside of the body’s cells such as bacterial toxins, pollen, and dust
Where are endogenous antigens produced?
are produced inside of the body’s cells such as viral proteins, abnormal proteins of cancerous cells
What is the major histocompatibilty complex?
An individual has a family of genes on chromosome number six called major histocompatibility complex that codes for proteins that act as “self-antigens”.
Where are MHC-1 proteins found?
are found on the plasma membrane of all body cells, except one’s erythrocytes
Continually synthesized by cell and transported to its plasma membrane
Where are MHC-2 proteins found?
occur only on antigen-presenting cells
What is the function of MHC proteins?
help T cells recognize foreign antigens
What are antigen-presenting cells?
are B cells, macrophages, or dendritic cells that process and present exogenous antigens for destruction
How does an immune response begin?
the antigen-MHCP complex is inserted into the plasma membrane of the antigen-presenting cell
the antigen-presenting cell then migrates to lymphatic tissue to present the “displayed” antigen to T cells in order for an immune response to begin
How is an antigen-MHCP comples formed?
a foreign antigen is ingested by phagocytosis
digestive enzymes are used to split the antigen into fragments
the antigen fragments are joined with MHCP molecules
What is the function of interleukins?
coordinate the activities of various leukocytes that are involved in the immune response
What do lympokins form?
What do monokines from?
What does cell-mediated immunity require?
requires the activation of a small number of T cells by a particular antigen
What do cell-mediated immunity target?
Targets bacteria, cells infected with viruses, cancer cells
What happens when an antigen-presenting cell encounters a foreign antigen?
it presents it to a T cell which recognizes it and binds to the antigen fragments displayed by the antigen-presenting cell
What does activation also require?
Activation also requires co-stimulation by interleukins to prevent immune system from destroying healthy cells
What happens once a T lymphocyte is activatated?
it proliferates and differentiates into a clone of identical cells that can recognize the particular antigen and carry out the immune attack
What are the functions of Helper (TH) cells?
recognize an antigen-MHCP complex and secrete interleukins
They attract neutrophils and natural killer cells
They attract macrophages and stimulate phagocytosis
They activate T cells and B cells
What are the funcions of cytotoxic (TC) cells?
recognize foreign antigens combined with MHC-I proteins and become “killer” cells in order to deliver a “lethal hit” to the target cell
What is the function of perforin?
Perforin forms holes in plasma membrane of target cell, which causes cells to burst
What is the function of lymphotoxin?
Lymphotoxin activates enzymes within target cell that will destroy target cell's DNA
What is the function of tumor necrosis factor?
Tumor necrosis factor kills cancer cells
What is the function of regulatory (Treg) cells?
release interleukins that will inhibit T cell and B cell activity and "turn off" the immune response once the pathogen has been destroyed
What is the function of memory (TM) cells?
remain from a proliferated clone to recognize the original antigen
Programmed to recognize original antigen, so immune system can swiftly destroy pathogen before any symptoms of disease occur
Want to see the other 103 Flashcards in Chapter 21?JOIN TODAY FOR FREE!