07 - Innate Immunity

Question 1

What is immunology

Answer 1

study of the immune system and immune response (study of the body’s defense against infection)

Question 2

What is the function of the immune system

Answer 2

prevent infection and eradicate established infections (maintain homeostasis)

Question 3

What is immunity

Answer 3

resistance to disease

Question 4

What is the immune system

Answer 4

functional system (rather than organ system)
- array of molecules and trillions of immune cells that inhibit lymphoid tissues and circulate in body fluids

Question 5

What are primary lymphoid organs

Answer 5

where pluripotent stem cells divide and become immunocompetent (able to protect)
(where immune cells are born and develop)

red bone marrow and thymus

Question 6

What are secondary lymphoid organs/tissues

Answer 6

sites where immune cells continue their maturation and can connect with one another to initiate adaptive immune responses
(where immune responses occur)

lymph nodes, spleen, lymphatic nodules/follicles

Question 7

Describe red bone marrow
What does it do

Answer 7

in flat bones. epiphyses of long bones, bodies of vertebrae

pluripotent stem cells give rise to mature, immunocompetent B cells and immature (pre) T cells

Question 8

Describe the thymus
What does it do

Answer 8

bilobed organ located in the anterior mediastinum

between the sternum and the aorta

where immature T cells go to develop into mature T cells
(early in life lots of T cells but then gland gets smaller and smaller – protection of new T cells reduce)

Question 9

Describe the lymph nodes

Answer 9

small organs distributed throughout the body

along the lymphatic vessels - filters for lymph

places where cells of the adaptive immune system “meet up”
- site where innate immune cell that encountered a pathogen goes to alert adaptive immune system

Question 10

Describe the spleen

Answer 10

largest secondary lymphoid organ

one of its important functions is the removal of damaged/defective RBC (contains phagocytes)

sequester platelets (releases)

lymphoid organ: has WBC will detect if there are any pathogens/toxins floating in the blood

Question 11

Describe the lymphatic nodules

Answer 11

organized masses of lymphatic tissue
- aggregations of immune cells sitting right under the epithelial barrier waiting for something to come in

not surrounded by a capsule
- embedded in the walls of organs

commonly associated with mucosal surfaces (MALT)

Question 12

Describe the innate immune system

Answer 12

non specific - responds to anything that injured tissue

1st and 2nd line of defence
- 1. skin and mucous membranes
(continuity, fluids/secretions/ microbiome)
- 2. internal defenses (antimicrobial proteins, NK cells/phagocytes, inflammation, fever)

Question 13

Describe the adaptive immune system

Answer 13

highly specific (identifies a specific antigen)

3rd line of defence

specific cell types and/or proteins are generated that attack foreign substances
- has memory (conferring lifelong protection)
- humoral immunity (plasma cells)
- cellular immunity (T cells)

Question 14

Describe the first layer of defense

Answer 14

skin and mucous membranes (intrinsic barriers)
- physical (b/c continuity), chemical, biological

Question 15

What are the barriers of the first line of defense

Answer 15

skin

eye
- blinking, tears, lysozme

respiratory tract
- coughing, sneezing, mucus, haris, ciliary action, lysozyme

gastrointestinal tract
- stomach acid, peristalsis, normal flora (B - commensal bacteria that take up space on the epithelium that prevent nasties from attatching)

urogenital tract
- flushing action of urine (P), acidity of urine (C), lysozyme, normal flora, vaginal lactic acid

skin
- sloughing (generating new cells and getting rid of the old), structural barrier, sweat/sebum, lysozyme, normal flora

Question 16

Describe the second layer of defense
What are the cells and factors

Answer 16

non specific line of defense when pathogens penetrate the surface barriers

cells & factors:
- antimicrobiral proteins
- natural killer cells
- phagocytes
- imflammation

Question 17

What are antimicrobial proteins

Answer 17

enhance innate defence by attacking microorganisms directly or hindering their ability to reproduce

• interferons (small secreted proteins that interfere with viral replication –> secreted by host cells)
• complement system (cascade (already present) of interacting plasma proteins that
  1. promote phagocytosis of phathogens
  2. cause cytolysis of bacteria (poke holes)
  3. enhance inflammation (vascular response – allows WBC to go out))
• iron-binding proteins (inhibit bacterial growth by binding iron
• antimicrobial proteins (short peptides with broad spectrum antimicrobial activity)

Question 18

What are natural killer cells

Answer 18

unique group of defensive cells

large, grandular lymphocytees

found in blood and tissues

can kill tumour and virally infected cells and dock with the cell and tell it to die using:
- perforin (make a hole in the cell)
- granzyme (promotes break down of DNA in the cell –> apoptosis)

attack cells that display activation receptors that lack inhibition receptors

from the same lineage as adaptive cells (lymphocytes) but part of the innate response
- no immunological memory, doesn’t get better every time

Question 19

What do phagocytes do
What are the phases

Answer 19

engulf foreign microbes and/or debris

phases:
1. chemotaxis: follow chemical trail to site of damage/infection
2. adherance: attachment to pathogen/debris
3. Ingestion: phagosome interalizes pathogen/debris
4. Digestion: phagosome fuses with lysosome that contains enzymes to break down proteins, lipids,… (H2O2, O2-, OCl-)
5. Killing/elimination
washed away by lymphatics

Question 20

What are the types of phagocytes

Answer 20

neutrophils
- most abundant leukocyte (WBC) in blood
- major component of pus (short life span)
- 1st phagocyte to move from blood to tissue during an inflammatory response (not present in healthy tissues - normally in blood sleeping, only activates when needed) –> do collateral damage

macrophages
- begin as monocytes in the blood
- move into tissues and mature into macrophages (big eaters)
- long life span
- reside in tissues, wander tissues looking for debris/invaders –> release cytocines to signal other things to come in or tell adaptive tissues to help)

dendritic cells
- tissue-resident (long lifespan)
- antigen-presenting cell (take whatever they encounter and take it to t-cells and b-cells to tell to kill)
- bridge gap between innate and adaptive immunity)

Question 21

How do phagocytes recognize the pathogens they need to kill

Answer 21

• use pattern recognition receptors (PRRs) to “see” pathogen-associated molecular patterns (PAMPs) –> encoded in our DNA
• PRR binds to PAMP –> generates a signal that stimulates the phagocyte
• signals through some receptors causes the secretion of pro-inflammatory cytokins (talk to other immune cells, blood vessels, endothelial cells…)

Question 22

What is inflammation

Answer 22

non-sepcific, defensive response to any tissue damage (Doesn’t have to be a pathogen)

delivers effector molecules and cells to the site of infection to assist in killing microbes
- stimulates and assists the immune systen
- prepare site for tissue repare
- very localized

Question 23

What are the three stages of inflammation

Answer 23

1. vasodilation and increased permeability of blood vessels (vascular response)
2. emigration of phagocytes from blood to the infected site (cellular response)
3. tissue repair (healing)

Question 24

What is the intial response of inflammation

Answer 24

damaged cells signal that something is wrong “chemical alarm”
- inflammatory mediators released into the extracellular fluid

resident macrophages become activated (PRRs)
- phagocytose pathogens
- release cytokines and chemokins –> signal the kind of help needed as well as directions

resident mast cells release potent inflammatory mediators
- histamine (major product)
- contribute to many aspects of the inflammatory response (vasodilation and increased vascular permeability)

within the first hour, see an influx of neutrophils and monocytes (immature macrophages)

Question 25

What are the signs and symptoms of inflammation

Answer 25

inflmmation usually localized and self-limiting (turn off by itself)

1. redness (rubor/erythema) - due to increased blood flow
2. heat (calor) - due to increased localized blood flow and cellular activity
3. swelling (tumor/edema) - due to increased vascular permeability - cells/fluids/prtoeins collect in the tissue
4. pain (dolor) - due to the swelling (stretching) and the release of neurotramitters and other chemical mediators (bradycardin..)
5. loss of fucntion (funcio laesa) - due to swelling and the release of neurotransmitteres and other chemical mediators

Question 26

What happens to blood vessels during inflammation

Answer 26

released mediators change local blood vessels
- increased vascular diameter: increased local blood flow
- reduction in blood flow velocity: gives cells a change to bind
- increased vascular permeability: cells leave blood and enter site of injury
- blood and fluid exit into the tissues: cause of edema
- immune cells emigrate/migrate/extravasate from the blood vessels to the tissue to help eliminate injurious agents

clotting of micro-vessels prevents spread of infection (trapping)

Question 27

What is fever

What is the cause

Answer 27

abnormally high body temperature
- systemic response to invading microorganisms

body’s response to infection is more widespread

many cytokines (pyrogens) that they spill into the blood and get to hypothalamus and signals massive infection
- hypothalamus raises set point for temperature

Question 28

How does fever help

Answer 28

mild to moderate fevers are useful adaptation to infection
- immune cells work harder and faster
- sequestration of iron and zinc by the liver and spleen
- bacteria need these minerals to multiply

pathogens and viruses can’t replicate in conditions

(excess heat denatures proteisn and enzymes can lead to brain lesions)