Public Health Lectures 7-10
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90 terms
Terms | Definitions |
|---|---|
 immunity | resistance to disease, specifically infectious disease |
| immune system | the collection of cells, tissues, and molecules that mediate resistance to infection |
| immunology | the study of the immune system and its responses to invading pathogens |
| functions of immune system | 1-prevent infection/disease (recognize invading organisms/antigens, prevent their proliferation and spread) 2-eradicate established infections |
| primary (central) lymphoid organs | bone marrow and thymus: bone marrow is only place in body to produce lymphocytes and thymus helps enhance maturation of lymphocytes (thymus active in young children and neonates) |
| secondary (peripheral) lymphoid organs/tissue | lymph nodes are strategically located, the spleen filters blood and blood-borne organisms, mucosal lymphoid tissue (tonsils, adenoids, Peyer's patches) located near respiratory and gastrointestinal tracts |
| antigens | antibody inducing, foreign, non-self substances that are recognized and responded to by lymphocytes |
| hemopoietic stem cells | all blood cells (RBC, WBC) originate in the bone marrow as stem cells |
| 2 lineages | lymphoid lineage: B lymphocyte, T lymphocyte myeloid lineage: phagocytes |
| basic principle of immunity | the immune system must be able to differentiate between material that is a normal component of the body (self) and material that is not native to the body (non-self) |
| innate immunity | aka native, nonspecific, or natural immunity -initial immediate defense against invaders, quick but less effective, it is non-specific |
| adaptive immunity | aka specific, or required immunity -later, more effective defense against infection, results from previous exposure or a trained immune system |
| first line of defense | innate immunity: epithelial barriers, specialized cells (enzymes in tears) and substance present in epithelia, anatomical (skin) mechanical (cilia in respiratory tract) physiological (lysosomes) |
| second line of defense | -phagocytes, natural killer cells, complement -specifically recognize and react against microbes but not against non-infectious foreign substances -cells that have receptors on cell membrane that bind with foreign ells then bring them to phagocytes or vice versa |
| third line of defense | adaptive immunity: since pathogens have evolved to resist innate immunity (first 2 lines) we need adaptive immunity |
| leukocytes (white blood cells) | phagocytosis- indiscriminate engulfment (engulfs anything non-native to the body) with help of neutrophils (polymorphonuclears) immune surveillance- NK cells active |
| commensals | bacteria that protects us by taking up space that bad bacteria would otherwise try to occupy |
| lymphocyte maturation | B cells are educated in bone marrow (any part of body that produces lymphocytes) and T cells in the thymus- edu involves acquiring specific lymphocyte receptors and eliminating cells that are anti-self- after edu cells are "immunocompetent" and mve to secondary lymphoid organs to perform immune surveillance |
| immune recognition | mature B and T cells in lymph nodes and nodules, spleen: B recognizes native antigen, T recognizes processed antigen when MHC presents bound peptide-antigen |
| characteristics of adaptive immunity | adaptation: recognize and respond to any particular pathogen that invades the body specificity: lymphocytes involved can recognize antigens that are specific to each pathogen memory: some T and B cells can remember the pathogen meaning upon another exposure can respond efficiently against it |
| humoral immunity | antibody-mediated immunity: antibodies are produced by B lymphocytes and are secreted into circulation in order to neutralize and eliminate microbes and toxins present OUTSIDE cells (defends against extracellular pathogens (bacteria in bloodstream) and can recognize different types of antigens (proteins, carbs, lipids) and the native antigen |
| cell-mediated immunity | mediated by T lymphocytes some of which activate phagocytes to destroy microbes while others kill any host cell harboring infectious microbes. the T lymphocytes recognize only protein antigens and the processed antigens that are INTRACELLULAR |
| lymphocytes | specific recognition of antigens (B mediate humoral, T mediate cell-mediated, NK are innate) |
| antigen-presenting cells | capture antigens to display to lymphocytes ex. macrophages |
| effector cells | eliminate antigens |
| antigen | the initiator and driving force for all adaptive immune responses |
| clonal selection | antigen selects the clone (cell lineage) of lymphocytes with complementary receptors leading to proliferation of cells that recognize a specific antigen |
| antibodies | unique molecules with specific reactivity to antigenic sites or epitopes, important for humoral immunity, belong to one of five classes: IgM, IgG, IgA, IgE, IgD |
| clonal expansion | B cells expand to form either plasma cells (free antibodies into circulation) or memory cells (watchdogs) |
| steps of humoral immunity | neutralization: block attachment and invasion of host cells, coding complement activation: series of plasma proteins that complements antibodies in fighting microbes opsonization: enhanced phagocytosis of bacteria |
| antibody-dependent cellular cytotoxicity | ADCC kills target cell with aid of antibody |
| cytotoxic T cells | destroy virally infected cells and tumor cells and are involved in transplant rejection |
| memory T cells | a subset of antigen-specific T cells that persist long-term after an infection has resolved |
| suppressor T cells | regulatory T cells that keep the immune system in balance |
| T helper cells | assist other cells! activate macrophages and cytotoxic T cells and assist with B cell maturation -become activated when presented with peptide antigens by MHC molecules and once activated they divide rapidly and secrete small proteins called cytokines that regulate or assist in the active immune response |
| cytokines | small proteins secreted by helper T cells that regulate or assist in the active immune response |
| desirable consequences of immunity | natural (innate) resistance, adaptive-naturally acquired immunity, adaptive-artificially acquired immunity (vaccines) self/non-self discrimination |
| undesirable consequences of immunity | hypersensitivity (over-response), autoimmunity (breakdown in self/nonself discrimination where body gets confused and attacks self), transplant rejection |
| hypersensitivity | -antigen that we shouldn't react to but the immune system initiates abnormal, hypersensitive reaction (autoimmunity) -or immunodeficiency: dangerous microorganism let into the body without immune response |
| 4 Types of Hypersensitivity | Type 1: most important, atopic/allergic disorders (IgE), immediate type hypersensitivity involving mast cell degranulation, ex. hay fever, asthma Type 2: cytotoxic reactions, cell death, ex. blood reactions Type 3: immune complex reactions, antigen/antibody complexes, ex. rheumatoid arthritis Type 4: memory T helper cells, overstimulation of macrophages forming granulomas |
| Allergies (Type 1) | immune system responds to allergen (IgE antibodies induced against allergen, mast cells release cytokines, induce inflammatory response) |
| clinical manifestations of Type 1 Hypersensitivity | allergic rhinitis, sinusitis, hay fever, food allergies, bronchial asthma, anaphylaxis (caused by drugs, bee stings and results in rapid fall in blood pressure and airway obstruction) |
| mast cell degranulation | a mast cell is a resident cell of several types of tissues and contains many granules rich in histamine and heparin |
| pathogenesis of Type 1 | production of IgE antibodies in response to antigen, binding of IgE to Fc receptors of mast cells, crosslinking of bound IgE by antigen (mushroom effect), release of mast cell mediators of inflammation |
| autoimmunity | during edu B and T lymphocytes recognizing self antigens are eliminated by apoptosis of clones causing a breakdown in self/nonself recognition so immune system attacjs own tissues leading to inflammation |
| clonal deletion | get rid of T cells |
| B cells | must bind to antigen, must get signal from T cell that it is a foreign substance |
| why study microbiology | impact on human health, balance of nature, environmental, industrial, agricultural |
| Pasteur's Epic Experiments | proved that no living things arise by spontaneous generation and that microbes are everywhere and the growth of microbes causes dead plants and animals to decompose and food to spoil |
| germ theory of disease | robert koch proved the theory that microbes cause disease and specific microbes cause specific diseases |
| microbes | organisms too small to be seen with the naked eye so are usually visualized by microscopy |
| medical microbiology | the study of disease-causing organisms, the host response to infection, the diagnosis, treatment, and prevention of microbial diseases |
| categories of microbes | viruses (neither pro nor eu), bacteria- including Rickettsia (pro), protozoa (eu), fungi (eu) |
| viruses | a set of genes packaged in a protein coat, not a cell, may be covered by lipid membrane derived from host cell, strictly intracellular organism, nucleic adic is either DNA or RNA never both, replicate using cellular machinery, some infect bacteria |
| prokaryotic cells | simple cells, no nucleus or organelles, reproduce by dividing into 2, bacteria are smallest living cells (1 piece of DNA, some contain plasmids-extra-chromosomal autonomous, self-replicating circular pieces of DNA) |
| bacterial classification | phenotypic classification (gram stain, culture characteristics, biotyping, serotyping, antibiogram, phage typing) and genotypic classification (nucleic-acid based methods can be used to rapid identification of organism and molecular fingerprinting) |
| serotyping | subdivide species based on the kind of cell surface antigens present |
| biotyping | based on chemical reactions |
| genotyping | based on genetic differences |
| principle of gram stain | one of the most important tests in microbiology it is used to identify bacteria, primary stain is usually crystal violet- the microorganisms that retain primary stain look purple brown and are gram positive the ones that do not and are red are gram negative; basic principle is the properties of certain bacteria cell walls to retain the crystal violet dye, the cell walls for gram positive organisms have higher peptidoglycan and lower lipid content than gram negative |
| acid fast stain principle | discovered by Ziehl this test demonstrates that certain bacteria stained with hot fuchsin resisted decoloration with alcohol (acid fast organisms); acid fast characteristics are due to high lipid and wax content, counter stain is methylene blue |
| rickettsia | obligate intracellular gram-negative rods that produce a distinct category or disease (endemic and epidemic typhus, rocky mountain spotted fever), classified as bacteria but behave like viruses |
| eukaryotic cells | nucleated cells, mitotic division, organelles present, nuclear membrane present, multiple chromosomes |
| eukaryotic microbes | fungi: yeasts and molds, mostly free-living, eukaryotic cell structure with rigid cell wall protozoa: single-celled parasites, mostly free-living, sexual or asexual reproduction |
| flagella | long, coiled structures made up of flagellin protein responsible for motility of bacteria, permit chemotaxis, cell surface-exposed flagella can be highly antigenic |
| fimbria (pili) | made up of pilin protein, thinner and more numerous than flagella; function as adherence factors and for the transfer of genetic material between bacteria |
| capsular polysaccharide | capsule is usually made of polysaccharide, major virulence factor but poorly antigenic, visualized by India ink technique (to see if it is a gelatinous capsule), promotes adherence to host cell surfaces and other bacteria |
| medical importance of spores | resistant to heat, desiccation, radiation, and disinfectants, metabolically inactive, can become vegetative once in the body |
| how are microbes detected | microscopy (light, dark, fluorescent, electron), culture, antigen detection, antibody detection by serology, nucleic acid detection |
| where are microbes found | everywhere! |
| determinants of outcome of host-pathogen interactions | virulence of organism, site of exposure, host's ability to respond to the organism |
| mutualism | symbiotic association in which both members benefit |
| commensalism | symbiotic association in which there is no apparent benefit or harm to either member (commensals are normal flora) |
| parasitism | symbiotic association in which one member lives that the expense of the other member |
| good of bacteria | help us digest our good, produce vitamins, and occupy niches that would otherwise be available for competing pathogens |
| epidemiological triad | agent, host, environment (disease results from interaction of the three) |
| transmission of infection | 1. spores produced by some bacteria and fungi are very resistant to drying and remain in enviro 2. gram positive organisms are well adapted to surviving on skin surfaces so stay on hands 3. gram negative organisms are adapted to surviving in fluids like water supplies 4. some thrive under conditions of poor hygiene so faecal-oral spread 5. fragile organisms require intimate contact |
| Koch's postulates | 1. the organism should be found in all cases of the disease and should be present in every single one of the lesions of the disease 2. it should be grown in pure culture on artificial media 3. inoculation of the pure culture should result in a similar disease 4. it should be possible to recover the agent from the lesions of the experimental disease THUS can prove that a particular organism is the cause of a particular disease |
| invasion and toxin production | the 2 main mechanisms of disease production by bacteria |
| determinants of virulence | the characteristics that allow a bacterium to produce disease |
| bacterial exotoxins | secreted outside the cell, act on cell surface by binding to certain receptors or forming pores in the cytoplasmic membrane |
| bacterial endotoxins | bound to cell membrane, usually in gram negative bacteria, very powerful toxins |
| virulence determinants: capsule | loose, relatively unstructured network of polymers on the bacterial surface, usually polysaccharide |
| 3 mechanisms of immune invasion | 1. antiphagocytic 2. decreased cell lysis by complement components 3. some capsules mimic host polysaccharides |
| how do organisms escape the immune system | extracellular pathogens (phagocyte avoidance mechanisms), intracellular pathogens (ability to survive within host cell) |
| avoiding phagocytosis | have capsules, produce toxins, produce extracellular enzymes, can cause antigenic variation |
| antigenic variation | changes in the amino acid composition of a surface protein |
| phase variation | switch on or off the expression of a bacterial cell component altering composition of cell wall |
| outcome of infection balance | pathogen's virulence, host immune integrity and response, pathogen's ability to escape immune response, medical intervention |
| mechanisms of evasion of host defenses | -maintain nutrition, secrete proteins that steal iron from host, capsule inhibiting phagocytosis, staphylococcus and streptococcus use enzymes to destroy leukocytes and macrophages, trypanosoma undergoes antigenic variation, HIV infects and destroys the cells of the immune system |
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