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98 Cards in this Set
- Front
- Back
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portal of entry
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Method by which the bacteria enters the body
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parenteral route
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Entry of organism through a deep bite or wound
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LD50
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Lethal dose (how many microorganisms to be lethal) for 50% of the population, a way of measuring how lethal a given organism is. Usually a measure of toxins produced by the microorganism.
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ID50
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Infectious dose (how many microorganisms to be infectious) for 50% of hosts. The smaller the ID50, the more virulent the organism (e.g. Hepatitis B has an ID50 = 1: in 50% of people, even just 1 Hep. B virus introduced into their system will result in infection.)
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Adherence
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Means of attachment by microorganisms to host cell
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ligands/adhesins
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Molecules found on the microorganism that bind them to the host cell
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receptors
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Molecules found on the host cell (in eukaryotes, host cell membrane) that microorganisms will adhere to via attachment through their ligands
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coagulase
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Enzyme that aids in microbial invasion, by clotting (coagulating) proteins surrounding an infection, preventing phagocytes from responding
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kinase
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Enzyme that dissolves blood clots, to allow microbes to move through clotted tissue
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hyaluronidase
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Enzyme that digests connective tissue, destroying cells
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collagenase
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Enzyme that destroys collagen (a type of connective tissue)
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Antigenic variation
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Method of avoiding specific immunity, by allowing rapid genetic changes (e.g. Trypsanoma species)
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invasins
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Method of rearranging the cytoskeleton to allow passage through cell junctions, allowing movement directly from cell-to-cell (intracellular movement)
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leukocidins
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Membrane-disrupting toxins that target phagocytic WBCs
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siderophore proteins
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Proteins released by bacteria that take iron away from iron-transport proteins circulating in the host (deplete host nutrients, and interrupts cell metabolism since iron plays a role in enzyme & coenzyme activity); once iron is bound to siderophore, siderophore receptors on bacteria are able to draw the iron into the bacterial cell.
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Toxin
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Any molecule poisonous to host system. Usually the primary factor contributing to the pathogenicity and virulence of a microorganism. Can cause damage to cell membranes, inhibition of cell metabolism (e.g. inhibit protein synthesis), and may produce fever, cardiovascular disturbances, diarrhea, shock.
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Toxigenicity
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The ability of a given organism to produce toxins
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Toxemia
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Presence of toxins in the blood
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Exotoxins
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Proteins produced inside bacteria as part of their growth & development, and then released to the outside of the cell to instigate toxic effect.
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Type I – superantigens
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Exotoxins which nonspecifically trigger TH proliferation, that results in release of cytokines by TH cells which induce a massive systemic response, including fever, nausea, vomiting, diarrhea, shock (e.g. Toxic Shock Syndrome Toxin, Staphylococcal toxins, Enterotoxins)
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Type II – cytolysins
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Exotoxins which result in lysis of host cell by disrupting the membrane of specific cells (e.g. leukocydins, hemolysins (specifically produced by Streptococcal organisms are Streptolysins))
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Type III – A-B toxins
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Exotoxins with two-portion proteins (A-B): A-component is active effector portion; B-component is portion that binds to affected cell. Includes diphtheria toxin (inhibits protein synthesis in affected cells), botulinum & tetanus toxin (inhibit the release of neurotransmitters at nerve/muscle endings), Cholera toxin (considered enterotoxin, causes severe diarrhea resulting in release of 10-20 liters of fluid daily)
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Endotoxin
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Lipopolysaccharide-derived toxin released in lysis of Gram-negative bacteria
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lipid A
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Endotoxin in lipid portion of LPS of outer membrane (present only in Gram-negative bacteria)
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Toxoid
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Denatured toxin that can still stimulate an immune response (antibody production) without causing toxic effects; used in vaccinations & booster shots (e.g. Tetanus shot is tetanus toxoid, not tetanus bacteria)
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Antitoxin
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Antibodies produced in response to toxin presence that can bind to toxin to aid in neutralizing its effects; can be used as a treatment against the presence of toxins in the body
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Pyrogen
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Any toxin that causes fever
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interleukin-1
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Cytokine released by macrophages after phagocytosis, that stimulates hypothalamus to produce excess prostaglandins, resulting in fever and chills
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tumor-necrotizing factor (TNF)
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Factor released by macrophages after phagocytosis that results in increased vasodilation & vascular permeability. Eventually can result in septic shock.
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septic shock
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Bacteria or bacterial toxins (or immune response to bacterial toxins, e.g. TNF) causing systemic shock: fluid leaves blood vessel walls in large amounts, decreasing blood volume and blood pressure, resulting in shock throughout the circulatory system
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Disseminated intravascular coagulation/ DIC
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DIC is another effect of TNF release. Creation of small clots called thrombi in a systemic infection of the capillaries (microthrombi) that stop blood circulation.
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Plasmids
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Independent small segments of DNA in bacteria that can code for antibiotic resistance
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Lysogeny
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Bacteriophage insertion into bacterial chromosome; may result in new proteins being coded by means of lysogenic conversion and specialized transduction
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lysogenic conversion
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Release of new proteins as a result of transcription of prophage, introduced into bacterial chromosome as a result of lysogenic infection
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Primary line of defense
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Includes skin, mucus membranes, tears, saliva, mucus, skin secretions (sweat and sebum (oily secretion lowers pH)), ciliary escalator, epiglottis, gastric juice (contains HCl), flow of urine and vaginal secretions.
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ciliary escalator
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Mechanical means of protection in primary line of defense
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lysozyme
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Enzyme in sweat, saliva and tears that destroys bacterial cell walls by breaking the bonds between NAG and NAM
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Normal flora
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Function as part of the primary line of defense by physically occupying space pathogens might adhere to in the intestinal tract, and by competing with invading bacteria through competitive inhibition
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phagocytosis
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Absorption and digestion of invasive cells by some leukocytes (notably macrophages, also neutrophils)
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leukocytosis
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Elevated levels of WBCs in blood count, indicate a recent infection
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leucopenia
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Lowered levels of WBCs in blood count, may indicate an infection affecting the WBCs themselves (e.g. release of leukocidins, or immune disorder such as AIDS)
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granulocytes
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Granular leukocytes, contain granules that have varying effects upon release in the immune response (e.g. histamine)
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neutrophils (PMNs)
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First responders to infection. Have segmented nucleus, granulated.
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Basophils
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Involved in histamine release. Dark blue/purple, unrounded nucleus
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eosinophils
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Granulocytes that have inhibitory effect against parasitic worms. Red color, u-shaped nucleus
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agranulocytes
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Leukocytes that do not contain granules (includes monocytes and leukocytes)
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monocytes
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Large, nonspecific agranulocytes that develop into macrophages in tissues. Second responders after neutrophils. Can be found in blood or fixed (e.g. liver, lungs, brain). Appear large and pale with u-shaped nucleus.
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lymphocytes
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White blood cells usually with specific immunity (recognize specific antigens, and have memory recognition of antigens upon reencounter). Also can include Natural Killer (NK) cells which are nonspecific cytotoxic lymphocytes.
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Macrophages
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Phagocytes derived from monocytes, which become macrophages once they leave the blood stream and enter into infected tissue. Also present fixed in certain tissues (liver, lungs, brain)
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Chemotaxis
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Attraction of phagocytes to an infected area because of chemical attraction to molecules called chemokines. Can be a result of damaged tissue releasing chemokines or bacterial chemicals being interpreted as chemokines
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Opsonin
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Any protein that coats a cell to be ingested by phagocytes, thereby enhancing phagocytosis
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Opsonization
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A process by which a cell or protein to be injested by phagocytes is coated to enhance phagocytosis
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Phagosome
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Vesicle in phagocyte containing ingested cell, formed after ingestion through the plasma membrane
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Phagolysosome
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Phagosome that has had lysosome fuse with it to release digestive enzymes, thereby digesting the foreign molecule or cell
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Lysosome
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– vesicle containing powerful digestive enzymes (hydrolytic enzymes) and bactericidal substances within a phagocyte. When digestion is complete, the hydrolytic enzymes are released by the phagocyte, provoking additional inflammation in surrounding tissues.
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Vasodilation
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Inflammatory response of increased blood flow to area of infection; results in redness and heat
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Edema
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Fluid localization due to increased blood vessel permeability, resulting in swelling
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Margination
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Stage following infection in which monocytes and neutrophils migrate to the linings of blood vessels, to better flow into infected tissue
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Diapedesis/emigration
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Phagocytes squeezing through the blood vessel walls and into tissues to effect phagocytosis (also stage where monocytes become macrophages)
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histamine
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Chemical mediator (can be released by basophils) which can cause vasodilation and increased blood vessel permeability
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kinins
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Chemicals that can function in vasodilation, increased blood vessel permeability, and chemotaxis
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complement
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System of proteins that can be activated in a chain reaction, either by reacting to the presence of an antibody (C1q reacting to Ab on bacterial cell begins classical pathway) or simply due to the presence of certain complement proteins reacting to complex bacterial or fungal polysaccharides (C3b binding to a protected surface on bacterial cell begins alternate pathway). Eventually results in the formation of a membrane-attack complex that breaks down the cell membrane of invasive cells.
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Properdin
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A stabilizing protein added to the cumulative complement proteins forming the membrane attack complex
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Interferon
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Proteins produced by virally-infected host cells that function as anti-viral proteins, offering protection to surrounding cells against any invasive virus (surrounding cell biosynthesis cannot be taken over by an infecting virus to replicate)
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Acquired immunity/specific immunity
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Immunity that is developed in response to specific antigens by the specific immune defenses of the host (B cells, T cells)
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naturally acquired immunity
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Specific immunity provoked by a natural encounter with the antigen or with antibodies to the antigen
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Active naturally acquired immunity
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Creation of antibodies by the immune system provoked by a natural encounter with an antigen, most likely through the disease process
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Passive naturally acquired immunity
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Natural acquisition of antibodies before birth and in infancy, within the fetal placenta or the mother’s milk
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Artificially acquired immunity
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Specific immunity induced by artificial intervention
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Active artificially acquired immunity
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Creation of antibodies by the immune system in response to a vaccine (either dead pathogens, inactive toxins, or weak live strains of pathogens)
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Passive artificially acquired immunity
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Artificial acquisition of antibodies through an injection
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Humoral immunity
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Antibody-mediated immunity (B cell immunity)
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Cell-mediated immunity
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Specific immunity directed directly through cells (T cell immunity)
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B cells
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Cells originating in the bone marrow, that promote the specific immune response through the creation of antibodies directed against specific antigens
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T cells
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Cells originating in the thymus gland, that promote the specific immune response through direct interaction with infected cells
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antigen (Ag)
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Foreign molecules that promote specific immune responses, especially produced by pathogens. Defined by epitopes, which help to distinguish them when antibodies are produced as a response to their presence
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antibody (Ab)
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A protein produced by B cells in response to a specific antigen, that aids in the specific immune response; also called immunoglobins
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immunoglobulin (Ig)
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antibodies, globulin proteins built to react to the specific epitopes presented by a pathogen or foreign molecule. Produced by B cells. Most have a monomer structure, quaternary in nature, with two outer light chains and two inner heavy chains linked by disulfide bonds (exceptions are the pentameter IgM antibodies (linked by additional disulfide bonds and J chain) and dimmer IgA antibodies (linked by J chain and secretory component))
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antigenic determinant
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Aka epitope, that portion of an antigen recognized by the antigen-binding sites of an antibody. A foreign microbe may have many different epitopes on it, resulting in the creation of numerous specific antibodies in reaction to it.
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antigen-binding sites
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the variable regions of an antibody, that are created to react to a specific antigenic determinant
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Fab
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includes variable region that functional portion of the antibody molecule (the “branches”) that binds to antigen, is developed specifically in response to the antigen, and constant region that remains the same
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Fc –
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portion of antibody that does not bind to antigen (the “stem”); has a role in activating the classical pathway of the complement system (stimulates C1)
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primary Ab response –
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the initial creation of antibodies in response to a given infection or other exposure to antigen, characterized by a moderate level of IgM initially and then a subsequent higher level of IgG several days after
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secondary Ab response
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the creation of antibodies in response to the second exposure to a previously encountered antigen, characterized by a very high level of IgG antibodies as well as a moderate level of IgM (similar to a level seen in primary Ab response)
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titer
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a measure of antibodies in serum, which can be used as a measure of immunological memory to a given pathogen, toxin, or other antigen
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antigen-antibody complex
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the binding of antigen to antibody, that can have effects including agglutination (clumping of numerous antigens for easier ingestion by phagocytes), opsonization (coating of antigen-covered surface with antibodies to enhance phagocytosis), and neutralization (blocking of antigen from effecting a toxic effect, or by blocking viruses from attaching to host cells
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ADCC
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Antibody-dependent Cell-mediated Cytotoxicity, a special type of antibody response in which coating of the antigenic surface by antibodies allows for destruction of target cell from the outside (usually by eosinophils releasing lysozomal enzymes on surface of target cell, and by response from macrophages and NK cells); especially useful in killing large parasites such as worms.
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MHC antigens
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antigens presented in a complex with MHC proteins of the body, those proteins that are self-determinant and unique to each individual. Can be within a cell that contains MHC-I (most cells of the body except red blood cells have this protein) or bound with MHC-II in a complex, as presented by the antigen-presenting cells. Both TH cells and TC cells react to these different MHC antigen complexes (TH usually with MHC-II complex and APCs; TC with MHC-I complex from an infected cell)
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TH
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Helper T cells, which aid in specific immune response by stimulating B cells (usually TH2 cells) and cytotoxic T cells (usually TH1 cells) after stimulation by contact with antigen-presenting cells. Communication and costimulation is done through the release of specific interleukins
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CD4
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surface molecule on TH cells that differentiates them from TC cells; also serves as a co-receptor for the antigen when interacting with antigen-presenting cells
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Antigen-presenting cells
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cells that can stimulate TH cells by presenting an antigen bound up with an MHC-II complex; include dendritic cells, macrophages and B cells
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TC
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Cytotoxic T cells, that directly kill infected cells presenting a specific MHC-I antigen complex. Their effector function is to kill by apoptosis, whereby the TC cell attached to an infected cell releases perforins that make holes in the cell membrane, and through these holes release penetrating granzymes that cause the infected cell to digest itself without inducing cell lysis. (If cell lysis had been induced without granzymes, it could result in the release of infectious viral particles, for example.)
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CD8
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surface molecule on TC cells that differentiates them from TH cells; also serves as a co-receptor for the antigen when interacting with infected cells presenting a specific MHC-I antigen complex
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NK cells
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natural killer cells, that do not respond to specific antigens but instead are triggered to induce apoptosis (in the same manner as cytotoxic T cells) by the absence of expression of MHC-I.
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Cytokines
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chemical messengers of the immune system; includes interleukins
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Dendritic cells
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Cells in lymph nodes and dermal skin; granular and function as antigen-presenting cells
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IL-1
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interleukin 1, cytokine released usually by antigen-presenting cell that costimulates TH1 cells already attached to MCH-II & antigen-fragment complex. Also produced by TH cells
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IL-2
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interleukin 2, cytokine released TH cells that helps to proliferate TH cells (costimulated by antigens) as well as B cells, helps to differentiate B cells, and aids in activating TC cells and NK cells
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