Immunity Flashcards
Define nonsusceptibility, including what factors it is and is not dependent on.
absolute protection against particular diseases associated with species characteristics; dependent on inherited physiologic and anatomic factors (such as diet and body temperature), NOT dependent on detectable antibodies
Define natural resistance.
ability of the individual to resist infection by means of normally present body functions; these functions are all subject to influence by nutrition, age, fatigue, stress, and genetic determinants
What are the two kinds of natural resistance and what are they composed of?
external (lactic acid in body secretions, cilia motion, urine excretion, stomach acid, lysozyme in tears and saliva, normal flora) and internal (cellular and humoral immunity, phagocytosis, inflammation)
What cellular mechanism are both natural and acquired immunity dependent on?
phagocytosis
What are the four basic steps in the phagocytic cycle?
physical contact between white cell and foreign particle -> formation of phagosome -> formation of phagolysosome -> digestion and release
What are opsonins?
serum proteins that attach to foreign substances and help prepare them for phagocytosis
What are the three important opsonin categories?
c-reactive proteins (CRP), complement components, and antibodies
What characteristic of phagocytic cells aids them in making contact with and initiating digestion of foreign particles?
they have receptors for immunoglobulins and complement components
By what process is undigested material excreted from a phagocytic cell?
exocytosis
Define phagocytosis.
an oxygen-dependent process by which a white cell kills and ingests foreign cells or particles
What substance is phagocytosis dependent on, and what does the process create to irreversibly damage the proteins of foreign particles?
oxygen-dependent; creates hypochlorite and hydroxyl ions
What three kinds of white cells fall under the category of granulocytes?
neutrophils, basophils, eosinophils
How do neutrophils move to areas of tissue damage in the inflammation process, and what is this mechanism called?
capable of moving from the circulating blood to the surrounding tissues by permeating the blood vessel walls (called diapedesis)
What are chemotaxins? Name these substances.
chemical messengers that cause migration of cells in a particular direction - these include complement components; coagulation cascade proteins; bacterial and viral products; and cellular secretions from mast cells, lymphocytes, macrophages, and neutrophils
What is chemotaxis?
process in which cells tend to move in a certain direction under the stimulation of chemotaxins
What is the most important role of eosinophils?
neutralizing basophil and mast cell products, and killing certain parasites
What substance is found in the granules of basophils and mast cells that, when released, cause hypersensitivity symptoms?
histamine
What type of white cell differentiates in the tissue to become a macrophage, and how long does it remain in the circulation before this differentiation takes place?
monocyte; ~70 hrs
What cell is the most active of all phagocytic cells?
macrophage
What are the six functions of macrophages?
microbial killing; tumoricidal activity; killing of intracellular parasites; phagocytosis; cell mediator secretion; antigen presentation
What are mast cells?
connective tissue cells of mesenchymal origin that resemble basophils, though they are larger, with a small round nucleus and more granules; widely distributed throughout the body with a lifespan of 9-18 months; participate in hypersensitivity reactions by binding IgE
What are dendritic cells?
cells covered with long membranous extensions - resemble nerve cell dendrites; mainly phagocytose antigen and present it to T-helpers; called “Langerhans” on skin and mucus membranes, “interstitial” in major organs; most potent phagocytic cell in tissue
What are toll-like receptors (TLRs)?
newly discovered molecules on human leukocytes and some non-leukocyte cell types that resemble toll, a protein originally discovered in fruit flies
Where are the highest concentrations of TLRs found?
on monocytes, macrophages, and neutrophils
How many different TLRs are there in humans?
11
How do TLRs work?
each receptor recognizes a different microbial product; once this receptor binds to its specific substance, phagocytosis is stimulated OR cytokines are produced
What the the name for a TLR’s specific substance?
ligand
What are acute phase reactants and where are they manufactured?
normal soluble constituents (factors) that increase rapidly because of infection, injury, or trauma to the tissue; produced primarily by hepatocytes in response to an inflammatory stimulus
What eight substances are considered acute phase reactants?
c-reactive protein (CRP), complement components, alpha-1 antitrypsin, haptoglobin, fibrinogen, ceruloplasmin, serum amyloid A, and mannose-binding protein (MBP)
What conditions can cause an increase in CRP, and how long does it take to see these increases?
4-6 hrs; found in bacterial infection, rheumatic fever, viral infections, malignant disease, tuberculosis, and following heart attack
What is CRP capable of, and what is its role in immunity?
opsonization, agglutination, precipitation, and complement activation; acts as a defense against pathogens until an antibody can be formed
Is CRP a specific or non-specific indicator of disease/trauma?
non-specific
What is complement?
series of 9 normally present serum proteins that mediate inflammation
How is complement activated?
bound antibody causes a sequence called the classical cascade, or bacteria triggers an alternate pathway
What are the major functions of complement?
opsonization, chemotaxis, and cell lysis
What is alpha-1 antitrypsin?
a major component of the alpha band when serum is electrophoresed; targets the proteases released from leukocytes (especially elastase, which degrades elastin and collagen)
What purpose does alpha-1 antitrypsin serve?
targeting of elastase is beneficial in chronic pulmonary inflammation (elastase damages lung tissue); also reacts with serine protease (found in the complement cascade or fibrinolysis) by binding with it, thereby completely inactivating and removing it from the area
What is the function of haptoglobin?
binds irreversibly to free hemoglobin released by intravascular hemolysis; because the complex is then cleared by the liver, free hemoglobin is not lost, the kidneys are protected from damage, and it prevents the loss of iron via urinary excretion
What is fibrinogen and what is its function?
most abundant coagulation factor in plasma; forms the fibrin clot at the site of a wound, which gives the wound strength and stimulates fibroblast proliferation and growth (two important factors in the healing process), and serves as a barrier to help prevent the spread of bacteria
What is ceruloplasmin?
primary transport protein of copper to cytochrome C oxidase (essential to aerobic energy production, which is needed for phagocytosis and wound healing); also serves as a scavenger of superoxide radicals generated by the phagocytosis process
What is serum amyloid A?
major serum protein thought to play a role in cholesterol metabolism; removes cholesterol from macrophages at sites of tissue injury
In what kind of infection is serum amyloid A slightly more increased?
bacterial
What is mannose-binding protein (MBP)? Include its other name.
also known as mannose-binding lectin; calcium-dependent opsonin capable of recognizing foreign carbohydrates such as mannose and other sugars
What is inflammation, including the four symptoms?
overall reaction of the body to injury or invasion by an infectious agent; symptoms include redness, swelling, heat, and pain
What are the four major events in the inflammation process?
increased blood supply to the affected area; increased capillary permeability; migration of white cells from capillaries to tissues; migration of macrophages
What is the role of chemical mediators in the inflammation process?
cause dilation of the blood vessels, which increases blood flow to the area, resulting in redness and heat
What causes the swelling and pain associated with the inflammation process?
increased vessel permeability allows fluid in the plasma to leak into the tissues
How long does the mobilization of neutrophils last in the inflammation process?
24-48 hrs, depending on the amount of chemotaxins present
What term is applied to inflammation that becomes prolonged?
chronic
What effect can prolonged inflammation have on the body?
loss of function; tissue damage attributed to specific immunity with infiltration of lymphocytes, or failure to remove bacteria and/or injured tissue
What is acquired immunity and what three categories can it be divided into?
resistance characterized by specificity for each individual pathogen and the ability to remember prior exposure; active, passive, and adoptive
What is active immunity?
active formation of specific antibody induced by exposure to an infectious agent itself or to one of its antigens; usually the result of natural infection or vaccination
What is passive immunity?
antibodies derived from another individual, such as those acquired in utero from maternal circulation, or post-partum from mother’s milk
How long does passive immunity last?
transient, usually only a few weeks or months
What is adoptive immunity?
produced by the transfer of antigen-sensitive (primed or immunocompetent) lymphocytes from an actively immunized donor to a non-immune or immunoincompetent recipient
Is adoptive immunity common?
no; it is not practical, due to the necessity of carefully genetically-matched cells
