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Flashcards in Midterm Deck (20):
1

Immune system

The body's defense system against invasion by microbes

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Latin word for immunity

Immunis

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Immunity

The state of protection from infection and disease

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When did the work immunology first appear in the index medicine?

1910

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Immune system function is to:

Recognize, respond, and eliminate foreign invaders

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Host defense system

Innate (natural) and acquired (adaptive)

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First line of defense

Anatomical/physical & chemical
Mechanical
Physiological
Biological soluble factors
Natural killer cells
Natural flora

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Anatomic/physical & chemical barriers


Skin, sebaceous glands, meibomian glands, mucus membranes, saliva, tears, mucus, twisted nasal passage, and short hair in the nasal passage.

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Physical barriers can be breached by:

Cut, wounds, burns, abrasions, insect bites, and needles

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Mechanical

Cili- located in the lower respiratory and GI tracts
coughing- involuntary, violent reflex by which air and mucus containing microbes are expelled from the mouth
sneezing- involuntary, violent reflex by which air containing microbes and mucus are expelled through the nose and mouth

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Physiological barriers

Body temperature- higher than 37C inhibits growth of some microbes. Fever is a natural defense mechanism
pH levels- stomach 2, skin 5.5, vagina 4.9. Low pH is particularly inhibitory to growth of fungi
O2 tension- o2 is important for microbe growth, anaerobic bacteria don't need o2 to grow
Enzymes- lysozymes in saliva, sweat, and tears degrade the peptidoglycan layer of bacterial cell walls
Interferons (IFN)- 3types IFNa, IFNb, IFNg. IFNa and IFNb can be produced by all cells in the body. IFNg can be produced only by T-cells and NK cells
Complement-blood proteins circulate in an inactive pro-enzymatic state
Natural killer (NK)- special type of leukocytes recognize cell surface changes that occur on some virally infected cells and some tumor cells. Bind to these target T-cells and kill them (cytotoxicity)
Normal flora- reduce the opportunity of pathogens to attach.

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Second line of defense

Endocytosis, phagocytosis, and inflammation

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Endocytosis

Pinocytosis
Receptor mediated endocytosis- cell takes in specific soluble substances. It has a specific receptor for them.

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Phagocytosis

Specialized white blood cells but not all are able to do Phagocytosis
Monocytes/macrophages
Polymorphonuclear leukocyte (PMN) neutrophils- bacterial infections, highest in #
Eosinophils- parasitic infections
Parasitic cells can ingest and degrade large insoluble particles that include microbes, cell degrees, etc.

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4 steps in process of phagocytosis

Chemotaxis
Migration
Ingestion
Killing

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Inflammation

Protective host response to tissue injury

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Steps in inflammation

1. Production of cell mediator – in response to tissue injury, mast-cells, basophils, and platelets release histamines and prostaglandins that cause vasodilation, and increase vascular permeability
2. Vasodilation– Causes increase in blood vessel diameter
3. Local increase in the number of erythrocytes manifests as redness (rubor). The increased velocity of blood flow causes heat (calor). Increases vascular permeability – leads to accumulation of fluid in the area that causes swelling (tumor) and pain (dolor). The pain results from the pressure on nerves from swelling, and production of bradykinins that stimulate pain receptors in the skin trapping microbes and attracting phagocytic cells. Accumulation of fluid and fibrin formation will trap microbe. Phagocytic (neutrophils and macrophages) cells will be attracted to the site.
4. engulfment and killing
5. Recovery– After phagocytosis microbes will be killed, and healing will proceed.

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Localized signs of inflammation

Redness (rubor)
heat (calor)
swelling (tumor)
pain (dolor)

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Characteristics

Specificity– the lines actions are specifically directed against the antigen that initiated the response.
Memory – third line can respond many years after the initial exposure because memory cells are produced.

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Immunology

Study of the immune system