Topic 13: The Body's defences

Question 1

What is innate immunity

Answer 1

Immunity that is naturally present and is not due to prior sensitization to an antigen

Question 2

what are innate immunity mechanisms found in blood?

Answer 2

A. White Blood Cells (Phagocytes, Eosinophils)

B. Antimicrobial Chemicals
(peptides, complement, interferons)

C. Processes (inflammation, fever)

Question 3

What is defensin

Answer 3

protein that protects host from bacteria by forming holes in bacterial membranes

Question 4

what are 3 functions of defensins

Answer 4

1) Defend from pathogens
2) Shape microbial flora
3) Protect stem cells

Question 5

Describe the mucociliary system

Answer 5

Mucociliary escalator

• The lower respiratory tract is lined with ciliated cells and goblet cells.
• Microbes get trapped in the mucus which is moved up to the throat.

Question 6

two parts of the mucociliary system

Answer 6

It is composed of two basic parts;

1. the mucus-producing goblet cells

2. the ciliated epithelium.


Question 7

what is phagocytosis?

Answer 7

when a phagocyte engulfs a microbe to destroy it

Question 8

what are the stages of phagocytosis?

Answer 8

Chemotaxis, Attachment/Adherence, Ingestion, Digestion, Release of Products

Question 9

what happens in chemotaxis phase?

Answer 9

The cell moves to the antigen (in response to microbial chemicals or cytokyines)

Question 10

what happens in attatchment/adherence phase?

Answer 10

Pseudopods are extended to enfold the microbe

Question 11

what happens in ingestion phase?

Answer 11

Membrane is wrapped around microbe (“Phagosome”)

Question 12

what happens in digestion phase?

Answer 12

Phagosome fuses with a lysosome (contains digestive enzymes)

Question 13

what happens in release of products phase?

Answer 13

Neutrophils release debris

Macrophages/dendritic cells transport some peptides from the microorganism to their cell surface

Question 14

what do eosinophils do?

Answer 14

Attach to surface of parasites & secrete toxins that may kill the parasite
Active eosinophils are involved in allergic reaction

Question 15

what are interferons?

Answer 15

Proteins that are released by infected host cells to inhibit viruses

Question 16

what is histamine?

Answer 16

Causes blood vessels to dilate and become more permeable

involved in inflammatory response

Question 17

what is sebum?

Answer 17

Low pH oil, inhibits many microbes (esp. fungi)

Question 18

what are dendritic cells?

Answer 18

Found just under the skin and epithelial layers

Engulf and digest invaders by phagocytosis

Question 19

what is the lacrimal apparatus?

Answer 19

Tears constantly wash the eyes and are collected in the nasal cavity

Question 20

what are phagocytes?

Answer 20

engulfs and destroys an invader by phagocytosis

Question 21

what is the complement system?

Answer 21

-Set of proteins that can trigger inflammation/fever, phagocytosis, or lysis of a pathogen

Question 22

what is inflammation?

Answer 22

A General non-specific response to tissue damage

Question 23

what is the inflammatory response?

Answer 23

Blood clotting signals release of histamines and other chemicals
Causes blood vessels to dilate and become more permeable

Question 24

what are lysozymes?

Answer 24

Small protein enzyme that cuts chemical bonds in cell wall peptidoglycan

Question 25

what are bacteriocins?

Answer 25

proteinaceous toxins produced by bacteria to inhibit the growth of similar or closely related bacterial strain(s)

Question 26

what are leukocytes?

Answer 26

white blood cells

Responsible for adaptive immunity and some aspects of innate immunity

Question 27

what are macrophages?

Answer 27

A phagocytic cell found in the liver, spleen, brain and lungs. Travels to all areas of the body to find and eat pathogens.

Question 28

what is MAC?

Answer 28

membrane attack complex - punches holes in cells

Question 29

what is vasodilation and what is the result?

Answer 29

the dilatation of blood vessels, which decreases blood pressure

Question 30

In order for a pathogen to cause disease, what three lines of defence does it have to get by

Answer 30

would have to get past the body’s three lines of defence

1. physical barrier
2. chemical/cellular responses
3. lymphocytes + antibodies

Question 31

What is innate immunity? Describe the first two lines of defence against pathogens

Answer 31

generally fast + non-specific

physical barrier + chemical/cellular responses

Question 32

Describe the methods of protection from pathogens provided by the skin

Answer 32

• skin secretes salts, sebum, and antimicrobials peptides which inhibit microbe growth
• microbes stick to dead skin cells and fall off with dead cells

Question 33

What are the components of blood.

Answer 33

RBCs, WBCs, platelets.

Question 34

Compare phagocytosis and non-phagocytic killing.

Answer 34

phagocytosis - eating microorganisms and dead/damaged cells
non-phagocytic killing
- natural killer cells: recognize and destroy infected cells
release cytolytic granules, induce
self-destruction of target cells
- eosinophils: attach to surface of parasitic worms and
secrete toxins

Question 35

describe fever and what increases the temp.

Answer 35

-abnormally high body temperature (Normal temp. 37°C)
-pyrogens increase temp
-ex. bacterial toxins, antibody-antigen complexes,
particles released by macrophages

Question 36

Describe the methods of protection from pathogens provided by mucous secreting membranes

Answer 36

epithelium secretes mucous, defensins, lysozyme, and phagocytes

Question 37

Describe the methods of protection from pathogens provided by mechanical defences

Answer 37

by mucociliary escalator, muscle contractions, lacrimal apparatus, flow of urine