Week 10: Host Defense

Question 1

innate immunity

Answer 1

• Physical and chemical barriers that exists to prevent infection from occurring in the first
place
• Non-specific, primary response mechanisms

Question 2

adaptive immunity

Answer 2

• Highly coordinated and specific response to a particular pathogen

Question 3

Anatomical Barriers:

Answer 3

Physical
• Skin
• Mucus
• Cilia
 Chemical
• Stomach acid
• Enzymes in tears
• Gland secretions

Question 4

Pattern recognition receptors (PRR)

Answer 4

recognize structures that are
shared by a class of microbes

Question 5

Toll-like receptors (TLRs),

Answer 5

expressed on Macrophages and Dendritic cells,

recognize different classes of microbial structures; 10 unique TLRs exist;

Question 6

When PRRs recognize their target molecule,

Answer 6

the macrophage or the dendritic cell will

release cytokines into the environment.

Question 7

The cytokines released by a macrophage or dendritic cell are specific
to

Answer 7

the type of PRR that was triggered, and thus is specific to the type/
class of pathogen.

Question 8

Interferons

Answer 8

signal to neighbouring cells that a viral infection is present. This shuts down
the neigbouring cells’ ability to synthesize proteins so that viral replication is inhibited
and spread is slowed in the area

Question 9

If the innate response isn’t sufficient to reduce the infection,

Answer 9

the

adaptive response is activated

Question 10

The bridge between the innate and the adaptive immune response
are the

Answer 10

antigen presenting cells (APCs).

Question 11

Now loaded with antigen,
the APC must present
antigen to a

Answer 11

lymphocyte to
stimulate an adaptive
response

Question 12

T cells develop from

Answer 12

lymphocyte precursor cells in the bone marrow

and complete their maturation in the thymus (hence, T-cell)

Question 13

There are two types of T-cells

Answer 13

• Th cells – Helper T-cells

* Tc cells – Cytotoxic T-cells

Question 14

If the TCR recognizes the antigen,

Answer 14

the

Th cell is activated

Question 15

Upon activation Th cells

Answer 15

Proliferate
Begin to produce effector cytokines that
support either the
• Cell-mediated response
• Humoral response

Question 16

For intracellular pathogens (viruses, intracellular bacteria)

Answer 16

Th cells will release IL-12, among other cytokines, which will activate Tc cells

Question 17

Upon activation, Tc cells

Answer 17

• Proliferate
• Circulate through the body and scan all
cells for antigen
• When the TCR recognizes its specific
antigen, it kills the infected host cell to
prevent further spread

Question 18

Upon activation, most Th and Tc cells become

Answer 18

effector T-cells;

however, some become memory T-cells

Question 19

Effector T-cells

Answer 19

Elicit the primary response and mediate their effects immediately

Question 20

Memory T-cells

Answer 20

• Do not respond immediately; are mostly inactive

* Long lived cell

Question 21

B cells develop from

Answer 21

lymphocyte precursor cells in
the bone marrow and complete their maturation in
there as well

Question 22

B-cells require two signals to

activate it

Answer 22

• Specific antigen-antibody interaction
• Cytokines secreted by Th cells;
generally IL-4 and IL-5

Question 23

Activated B-cells will proliferate and

develop into either:

Answer 23

• Effector B-cells; called plasma cells
which secrete antibodies
• Memory B-cells; long-lasting cells

Question 24

Neutralization

Answer 24

• Binds to the surface of pathogens, effectively

blocking their access to infect other cells

Question 25

Agglutination

Answer 25

• Because antibodies have two binding sites, they
can bind to two antigens. Clumping of several
antibody-antigen complexes is called
agglutination
• Pathogens stuck in these clusters are unable to
infect host cells

Question 26

Opsonization

Answer 26

• Antibodies have a binding site for phagocytic cells;
as a result they enhance phagocytosis of
antibody-bound antigens

Question 27

IgM

Answer 27

Initial antibody secreted by plasma cells

Question 28

IgG

Answer 28

• Follows IgM production, but is the type that is most
abundantly produced during a humoral response
• Due to its size it can cross the placenta and enter breast
milk; important in newborn immunity

Question 29

IgA

Answer 29

• Offers protection in the mucous membranes
• Tears, saliva, GI tract
• Can also enter into breast milk for newborn immunity

Question 30

IgE

Answer 30

• Most often associated with allergy

Question 31

inductive period

Answer 31

time between the
initial infection and the onset of the adaptive
response (usually measured by antibody
production)

Question 32

Regulatory T-cells (Tr cells) help to slow the adaptive

response after an infection is cleared

Answer 32

• Effector T-cells and plasma cells (effector B-cells) are
eliminated
• Memory T-cells and memory B-cells persist

Question 33

A secondary exposure to
the same pathogen
typically results in

Answer 33

faster and stronger
response due to the
presence of Memory T
cells and B cells

Question 34

Inactivated, or Heat-killed vaccine

Answer 34

• Made from killed pathogen
• Generally develops a weaker response and less protection
• Regarded as highly safe – no chance of mutation

Question 35

Attenuated

Answer 35

• Made from weakened pathogens
• Generally develops a more robust response, more memory cells and better long-term protection; but, in some cases they are
regarded as less safe. Since it is a live, albeit weakened, form of the pathogen there is always a slight risk that mutation could
result in infection

Question 36

Subunit

Answer 36

• Made from subunits of the pathogen (antigens/ proteins)
• Generally develops a weaker response and less protection
• Regarded as highly safe – no chance of mutation