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50 Cards in this Set
- Front
- Back
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Infection
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invasion or colonization of the body by pathogens, presence of pathogens in the body (ex. HIV+, HCV)
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Disease
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when the growth of the pathogens damages all or part of body so that it is incapable of performing normal functions (ex. HIV infection AIDS, HBV infection hepatitis)
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Normal flora
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• Organisms that normally colonize a host without causing disease
• Includes: bacteria, viruses, fungi, protozoa • Body cells = 1013 • Bacterial cells = 1014 ten times more than body cells • Microbes outnumber human cells 10 to 1 |
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Sites that harbor normal flora
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skin
upper respiratory tract most of GI tract, large intestine highest # outer opening of urethra vagina |
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Microbe-free anatomical sites
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All internal tissues & organs
Fluids within an organ or tissue blood urine in kidneys, ureters, bladder cerebrospinal fluid semen prior to entering urethra amniotic fluid surrounding embryo & fetus |
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Predisposing factors – make a person more likely to allow the microbes to overgrow & get sick
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old age & extreme youth
genetic defects in immunity AIDS surgery & organ transplants diseases: cancer, diabetes physical & mental stress other infections |
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Portals of entry
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Site where microbes enter the body
Skin Mucous membrane Parenteral- deposited under the skin or mucous membrane |
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Infectious dose
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Number of microbes required to initiate an infection
Varies with infectious agent It usually takes more than 1 to start an infection. 1 rhinovirus cold; RARE SITUATION 10,000 HIV HIV positive 10,000 bacterial cells gonorrhea 8,000-50,000 anthrax spores anthrax |
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Virulence factors
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Factors a microbe uses to invade and colonize a host. Pathogenic bacteria have more of these than bacteria of the normal flora.
Adherence factors Exoenzymes – dissolve host defense barriers, promote spread into deeper tissues Toxins – poisons antiphagocytic factors – help in avoiding WBCs |
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Adherence factors
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Fimbrae
Capsules spikes hooks flagella |
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Examples of a few Exoenzymes
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Mucinase – digests protective coating of mucous membranes
hyaluaronidase – digests hyaluaronic acid, which cements cells together coagulaeses – cause blood clots Kinases- break clots |
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Antiphagocytic factors
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leukocidins – kill WBCs
slime layers & capsules – make it difficult for phagoctyes to engulf bacteria Mycobacterium and Legionella may replicate within WBC |
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4 periods of disease
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Incubation- time from initial contact with microbe; microbe multiplies
Prodromal – microbe multiplies, appearance of first symptoms Invasion – microbe multiplies to high levels, exhibits greatest toxicity, becomes well established in target tissue Convalescent - mo are cleared, recovery |
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Portals of exit
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respiratory & saliva
skin scales feces urine urogenital tract blood |
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Reservoir of infection
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Primary habitat where a pathogen originates
either living organism or inanimate object provides pathogen with adequate conditions for Survival Replication Opportunity for transmission |
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3 types of reservoirs
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Human reservoirs - People with or without signs & symptoms
Animal reservoirs- contact with infected animals, wastes, or hides, or insects; animal may or may not have symptoms Zoonoses - diseases that occur primarily in animals & can be transmitted to humans Nonliving reservoirs- soil, water, food |
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Measures to prevent nosocomial infections
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Hand-washing
gloves gowns masks surgical asepsis – practices to maintain a microbe-free surgery medical asepsis – practices that lower loads of mo in patients, personnel & hospital |
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Most common sites of nosocomial infections
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Urinary tract infection
surgical wound infection lower respiratory tract infection bacteremia cutaneous infection |
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Koch’s Postulates
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Purpose: determine the causative agent of a disease
Find evidence of a particular microbe in every case of a disease. Isolate mo from an infected subject & grow it in the lab. Inoculate a susceptible healthy subject & observe resultant disease. Reisolate the agent from this subject. |
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Exceptions to Koch’s Postulates
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Bacteria and viruses that cannot be grown on artificial media - syphilis
Some diseases are caused by a variety of mo: diarrhea, pneumonia Some pathogens cause several different diseases: Streptococcus pyogenes Exclusively human diseases: no animal model, immoral to infect human with incurable disease. |
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Physical barriers at body’s surface
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skin pH 4 – acidic; layers of tightly packed cells
perspiration - flushes skin, high salt, contains lysozyme- degrades bacterial cell wall Saliva mucus traps mo ciliary escalator of lower respiratory tract moves continuously propelling dust & mo toward throat Stomach acid |
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2nd level -Innate Defense System
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Innate immunity serves as a rapid response system for detecting & clearing infections by microbes.
When an invader is detected, many signaling proteins are produced that induce inflammation & direct the body to mount a full-fledged immune response. Phagocytes – dendritic cells, macrophages, monocytes & neutrophils Engulf & destroy invaders. Take antigen to lymph node & present to the T cells. Some microbes may reproduce inside the phagocytes |
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5 types of leukocytes (WBCs)
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Neutrophils (55-90%) phagocytes
Monocytes (3-7%) differentiate into phagocytic macrophages after leaving the blood & going into tissues Eosinophils (1-3%) somewhat phagocytic, produces toxins against parasites Basophils (0.5-1%) involved in allergic response Lymphocytes (20-35%) B & T types, involved in specific immune response, Not phagocytic |
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Functions of the lymphatic system
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Route for return fluid to circulatory system
Drain off system inflammatory response renders surveillance, recognition, & protection against foreign materials |
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Lymph
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Formed when blood components move out of blood vessels into extracellular spaces & diffuse into lymph capillaries
plasmalike liquid carried by lymphatic system contains: water, dissolved salts & 2-5% protein transports WBCs |
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Lymph node
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small, bean-shaped organs stationed in clusters along lymphatic channels, large blood vessels
aggregations occur in armpit, groin, & neck Contains large numbers of B&T cells Filter lymph, allowing pathogens to encounter B & T lymphocytes |
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Inflammatory response
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The elements of the innate system work together
Inflammatory cytokines such as tumor necrosis factor (TNF) & IL-1 are released into the tissues, summoning beneficial cells & fluids into the injured area Causes: swelling, pain, fever, fatigue and malaise. |
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stages of inflammation
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tissue damage – complement & phagocytes act
Triggers blood vessels to dilate (vasodilation) & increase their permeability WBCs leave blood vessels, enter tissue and phagocytosis & more inflammation mediators released. If needed more inflammatory cytokines such as tumor necrosis factor (TNF) & IL-1 are released into the tissues, causing fever, fatigue and malaise. tissue repair |
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Functions of Inflammation
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Attract immune components to site of injury
Repair tissue damage, localize & clear away harmful substances Destroy microbe & block further invasion Inflammation may cause collateral damage where normal healthy host cells are killed |
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Fever
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Does NOT directly kill mo
Inhibits growth of temp sensitive mo Decreases amount of iron available, impeding bacterial nutrition Increase metabolism & stimulates immune reactions |
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Phases of phagocytosis
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Chemotaxis
contact & ingestion Lysosome fuses with vesicle killing, digestion of microbe release of debris |
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Interferon
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Protein secreted by a virus infected cell
Binds to neighboring cells and causes them to produce antiviral proteins that block virus replication Signals cell to apoptosis (suicide) if infected. Not virus specific Host species specific, (human interferon for humans, etc.) |
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Complement
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A group of 20 proteins present in the bloodstream in inactive forms
Cleavage of complement proteins activate them Functions: (OIL) Opsonization – coating with C proteins facilitates phagocytosis Inflammation – summons other immune cells into the area Lysis -may initiate membrane attack complexes that destroy cells & inactivate viruses |
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When microbes breach the barrier defenses
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Complement binds – opposonization, inflammation & lysis
Dendritic cells phagocytize & release cytokines. Activated NK cells, neutrophils, macrophages & interferon attack If large amounts of cytokines & dead cells are produced, dendritic cells exit the tissues & migrate to lymph nodes In lymph nodes, they present antigen to TH and B cells & signal the type of response needed. (Dendritic cells are like the “coach” & TH cells the “quarterback”) |
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The immune system has 2 divisions.
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The innate part acts near entry points into the body & is always at the ready.
If it fails to contain a pathogen, The adaptive division kicks in later by mounting a highly targeted attack against the specific invader. |
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The adaptive immune system
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Helper T cells –activate other T & B cells
Cytotoxic T cells – kill infected cells by secreting perforin B cells produce antibodies to Opsonize microbes Agglutinate microbes Neutralize microbes |
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2 branches of the adaptive immune system
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Humoral immune system- takes place in body fluids; B cells secrete antibodies that “attack” antigens
Cellular immune system – takes place between the T cells and antigens (infected, cancerous or other types of cells. |
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Antigen
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(foreign invader) a substance that is recognized as foreign or “nonself” by the immune system. May be a whole microorganism or a portion of it.
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Antibody
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(defensive weapon) a Y-shaped protein which is produced & secreted by B cells in response to a specific antigen. Antibodies bind to & contribute to the destruction
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Structural & chemical characteristics of antibodies
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Also called immunoglobulins
highly specific proteins that interact with only one antigenic determinant (epitope) on an antigen serve as antigen receptors for B cells each Ab has 2 identical binding sites for antigen a typical Ab monomer has 4 protein chains a. 2 identical Light (L) chains b. 2 identical Heavy (H) chains each H & L chains has a variable region & a constant region |
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variable region
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located at the end of the Y arms
account for ability to bind specific Ag thousands of possibilities |
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constant region
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located at the stem & lower parts of the Y arms
5 major types of constant H regions ( G,M,A,D,E) 2 major types of constant L regions ( kappa, lambda) stem of the Y called Fc region Fc can bind to host cells Fc of G & M classes of Ab can activate complement |
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Characteristics of each of the 5 classes of antibodies
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IgG
cross placenta & confer passive immunity to fetus trigger complement system IgM pentamer – 5 monomers & a J chain trigger complement system first antibody to appear after initial exposure to Ag 3. IgA high amounts are in mucous, saliva, & breast milk secretory IgA – dimmer- 2 monomers & a J chain & a secretory component main function is to prevent attachment of pathogens to mucous membranes 4. IgD acts as antigen receptor on B cells No known function in serum 5.IgE bound to mast cells & basophils by Fc end, serve as Ag receptors & binding causes release of histamine & chemicals allergies useful against parasitic worms |
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What happens after antibodies bind to antigen?
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Neutralization - block virus attachment to cell, block toxin's active site
Activation of complements(opsonization, inflammation, lysis) Agglutination - clumps Ag together -helps phagocytosis Opsonization -helps phagocytosis |
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Primary immune response
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Slower
Weak response Few specific B & T cells Few antibodies made |
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Secondary immune response
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Faster
Strong response More specific B & T cells Lots of IgG made quickly Basis for vaccines & booster shots |
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How does the Cellular Immune System distinguish between “self” and “nonself”?
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All body cells have Major Histocompatability Complex (MHC) class I proteins on their surfaces that mark the cells as “self”
Immune system tries to destroy anything that does not have class I proteins because they are “nonself”, or antigens |
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T cells
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Derived from bone marrow and mature in the thymus
Make up 70-80% of circulating lymphocytes Each has a T cell antigen receptor which recognizes a peptide bound to a self MHC molecule Do not recognize soluble, Extracellular antigen Antigen must be displayed on surface of an antigen presenting cell like a B cell or macrophage |
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4 Types of T cells
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Helper T4 Conductor of immune system
Cytotoxic T8 Destroy target cells on contact DH Allergic responses, kill cancer cells Suppressor Turn off immune responses |
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Cytokines
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Chemical messengers of the immune cells
Signal cells to move into area, become active, replicate, etc. used to communicate among WBCs Interleukin 1 (IL-1) Interferon (IFN) Tumor Necrosis Factor (TNF) |
