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Biology Semester 2 > Innate Immunity (pt.1) > Flashcards

Innate Immunity (pt.1) Flashcards

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1
Q

What is immunity

A

Immunity means protection and is taken as the body’s insensitivity to infectious and non-infectious agents

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2
Q

Immune system

A

The organs and cells implementing immunity

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3
Q

2 types of immunity

A

-Innate (non-specific)
-Acquired (specific)

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4
Q

Innate immunity

A

-Part of our defence mechanisms is ready to act against the pathogen even before it has appeared.
-It is activated immediately after the entry of a disease-causing agent (foreign body) into the body of the host.

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5
Q

Why is innate immunity non-specific

A

-It is directed against all pathogens in general and not against a specific one
-It includes several lines of defence that protect the organism and activates the mechanisms of acquired immunity.

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6
Q

What does innate immunity offer

A

A primary defense in all animals and sets the stage for adaptive immunity

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7
Q

What is adaptive immunity (vertebrates only)

A

-Recognition of traits specific to particular pathogens
-Lots of receptors are used
-Slower response

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8
Q

Barrier defenses

A

-Skin
-Mucous membranes
-Secretions

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9
Q

Skin

A

-Mechanical barrier
-Damage of the skin predisposes to infections

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10
Q

Mucous membranes

A

-Lines the digestive, respiratory, urinary and reproductive tracts
-Produces mucous
-Mucous secretion envelopes pathogens and prevents them from adhering to epithelial cells
-Cilla of the respiratory tract sweeps the mucous and any entrapped particles upwards

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11
Q

Secretions

A

Tears, saliva and urine wash away pathogens

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12
Q

How do body secretions create an environment that is hostile to many pathogens

A

-Tears, saliva and mucous secretions contain the enzyme lysozyme, which breaks down the bacterial cell walls
-Hydrochloric acid; in the stomach kills most pathogens
-Some of the pathogens die during the transition into the duodenum from “pH-shock”
-Secretions from oil and sweat glands give human skin an acidic pH that prevents the growth of many bacteria
-The intestines and vagina have a normal microflora that competes with pathogens

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13
Q

Internal defenses

A

-Cellular (by direct action of immune cells)
-Humoral (via proteins)

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14
Q

Cellular

A

-Intracellular killing of bacteria= phagocytic cells
-Extracellular killing= eosinophils and NK cells (natural killer cells)

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15
Q

The two main types of phagocytic cells in the mammalian body

A

-Neutrophils
-Macrophages

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16
Q

Neutrophils description

A

-Small
-Segmented nucleus
-Circulate in the blood; 1st barrier in limiting the inflammatory process
-Migrate through the capillary walls to the sites of tissue damage, where they engulf and destroy the pathogens
-Short-lived (from a few hours to 4 days)

17
Q

Macrophages description

A

-Larger
-Unsegmented kidney-shaped nucleus (mononuclear)
-Inactive in the blood vessels and stay there
-After passing into the connective tissue, they transform into macrophages
-Long-lived

18
Q

Mononuclear phagocytic system (MPS)

A

-After a short stay in the blood, monocytes settle in the tissue as resident (tissue) macrophages.
-In different tissues, they have different morphology and, accordingly, names.

19
Q

Tissue/Organ:
-Blood
-Lungs
-Liver
-Skin epidermis
-Bones
-Brain

A

Name of the MPS:
-Monocytes
-Alveolar macrophages
-Kupffer cells
-Langerhans cells (LCs)
-Osteoclasts
Microglia

20
Q

Mechanism of phagocytosis

A

1) Chemotaxis and adherence of microbe to phagocyte
2) Ingestion of microbe by phagocyte
3) Formation of a phagosome
4) Fusion of the phagosome with a lysosome to form a phagolysosome
5) Digestion of ingested microbe by enzymes
6) Formation of the residual body containing indigestible material
7) Discharge of waste materials

21
Q

How do phagocytes work

A

They recognise the overall appearance of the surface of a specific molecule from the pathogen, especially the type and density of carbohydrate residues

22
Q

What are pattern recognition receptors

A

The receptors responsible for recognition on the phagocyte

23
Q

The function of eosinophils and NK (natural killer) cells

A

It is used by the body when the object is too large for phagocytosis

24
Q

What are eosinophils

A

-They have many granules (lysosomes)
-They pour out the contents of the granules onto the object by exocytosis
-Eosinophils are the main weapon of innate immunity against helminths
-They are found in the blood and submucosal tissues, where the parasite is most likely to come from
-They are also activated in allergic conditions

25
Q

What are NK (natural killer) cells

A

-They kill by cytotoxicity (cytolysis)
-They have granules with a protein called perforin; it pours onto the target cell and forms pores in its membrane
-The NK cells also secrete a special proteolytic enzyme (granzyme) that enters the target cell through perforin pores and signals for apoptosis
-NK cells are a type of lymphocyte. They recognise virus-infected cells and some cancer cells through pattern-recognition receptors.

26
Q

The 2 main humoral protective factors of innate immunity

A

1) Blood-clotting; during injury that blocks the path of pathogens
2) The complement system; a set of proteins in the blood plasma with an extremely important role

27
Q

Similarities between the coagulation and complement systems

A

-Consist of plasma proteins synthesized in the liver
-Most of these proteins are proteases that are normally in the form of inactive precursors
-Their main function is to respond to a stimulus caused by external injury
-The stimulus causes their components to activate each other through limited proteolysis, forming a cascade

28
Q

What is inflammation (inflammatory response)

A

-Inflammation is the activation of innate defences (both cellular and humoral) at a site affected by injury/infection.
-Its main signs are; pain, temperature, redness or swelling
-Two types of cells of bone-marrow origin are responsible for inflammation; mast cells and basophils (basophilic granulocytes)

29
Q

What are mast cells

A

-Large, ovoid, connective tissue cells with a spherical nucleus and cytoplasm filled with large, intensely basophilic granules.
-Initially, they circulate in the peripheral blood as immature agranular cells. After migrating into the connective tissue, they differentiate and produce their characteristic granules.
-Mast cells contribute to the inflammatory response, as well as to the allergies.

30
Q

What are basophiles

A

-Basophils are granulocytes that circulate in the bloodstream and represent less than 1% of peripheral white blood cells (leukocytes)
-Share many features with mast cells, such as basophilic secretory granules.

31
Q

Major events in the inflammatory response

A

1) At the injury site, mast cells release histamines, and macrophages secrete cytokines. Some of these signalling molecules cause nearby capillaries to dilate, while others attract neutrophils.
2) Capillaries widen and become more permeable, allowing fluid containing antimicrobial peptides, as well as neutrophils, to enter the tissue. These immune cells digest pathogens and cell debris, allowing the tissue to heal

32
Q

What is systemic inflammation

A

-Throughout the entire body
-Caused by extensive tissue damage/severe infection
-Cells in injured/infected tissue secrete molecules that stimulate the release of additional neutrophils from the bone marrow.

33
Q

What is chronic (ongoing) inflammation)

A

Example; Crohn’s disease and ulcerative colitis, debilitating disorders in which an unregulated inflammatory response disrupts intestinal function

34
Q

What are interferons

A

-They are proteins that provide innate defence against viral infections
-Virus-infected body cells secrete interferon proteins that induce nearby uninfected cells to produce substances that inhibit viral replication.
They are very efficient in the control of viral infections such as colds and influenza

35
Q

General functions of interferons

A

-Signals neighbouring uninfected cells to destroy RNA and reduce protein synthesis
-Signals neighbouring infected cells to undergo apoptosis.
-Activates immune cells

Biology Semester 2 (3 decks)

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