Innate Immunity (pt.1)

Question 1

What is immunity

Answer 1

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

Question 2

Immune system

Answer 2

The organs and cells implementing immunity

Question 3

2 types of immunity

Answer 3

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

Question 4

Innate immunity

Answer 4

-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.

Question 5

Why is innate immunity non-specific

Answer 5

-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.

Question 6

What does innate immunity offer

Answer 6

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

Question 7

What is adaptive immunity (vertebrates only)

Answer 7

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

Question 8

Barrier defenses

Answer 8

-Skin
-Mucous membranes
-Secretions

Question 9

Skin

Answer 9

-Mechanical barrier
-Damage of the skin predisposes to infections

Question 10

Mucous membranes

Answer 10

-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

Question 11

Secretions

Answer 11

Tears, saliva and urine wash away pathogens

Question 12

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

Answer 12

-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

Question 13

Internal defenses

Answer 13

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

Question 14

Cellular

Answer 14

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

Question 15

The two main types of phagocytic cells in the mammalian body

Answer 15

-Neutrophils
-Macrophages

Question 16

Neutrophils description

Answer 16

-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)

Question 17

Macrophages description

Answer 17

-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

Question 18

Mononuclear phagocytic system (MPS)

Answer 18

-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.

Question 19

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

Answer 19

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

Question 20

Mechanism of phagocytosis

Answer 20

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

Question 21

How do phagocytes work

Answer 21

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

Question 22

What are pattern recognition receptors

Answer 22

The receptors responsible for recognition on the phagocyte

Question 23

The function of eosinophils and NK (natural killer) cells

Answer 23

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

Question 24

What are eosinophils

Answer 24

-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

Question 25

What are NK (natural killer) cells

Answer 25

-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.

Question 26

The 2 main humoral protective factors of innate immunity

Answer 26

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

Question 27

Similarities between the coagulation and complement systems

Answer 27

-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

Question 28

What is inflammation (inflammatory response)

Answer 28

-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)

Question 29

What are mast cells

Answer 29

-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.

Question 30

What are basophiles

Answer 30

-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.

Question 31

Major events in the inflammatory response

Answer 31

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

Question 32

What is systemic inflammation

Answer 32

-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.

Question 33

What is chronic (ongoing) inflammation)

Answer 33

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

Question 34

What are interferons

Answer 34

-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

Question 35

General functions of interferons

Answer 35

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