Week 5 - The Innate Immune System P2

Question 1

What are phagocytes

Answer 1

type of immune cell which identifies, engulfs and digests pathogens, dead cells and other foreign materials
- macrophages
- Neutrophils
- Mast cells
- dendritic cells

Question 2

What are granulocytes

Answer 2

Cells that contains granules in their cytoplasm
Type of white blood cell that includes:
- neutrophils
- eosinophils
- basophils

Question 3

What are macrophages

Answer 3

• type of white blood cell involved in the innate immune system + tissue homeostasis, repair, and activation of adaptive immune response
• digest and destroy invaders (phagocytosis)
• A monocyte which has entered tissue from the bloodstream

Question 4

What are monocytes

Answer 4

• type of leukocyte (white blood cell) found in the bloodstream
• acts as a precursor to macrophages and dendritic cells (when monocytes leave the bloodstream and enter tissues they differentiate into macrophages or dendritic cells)

Question 5

What are neutrophils

Answer 5

• type of white blood cell
• serve as body’s first line of defense
• function to engulf extracellular bacteria

Question 6

What are mast cells

Answer 6

• type of granulocyte
• releases histamine causing vasodilating during allergic reactions - causing swelling, itching and redness in the skin
• promotes inflammation
• allergic reaction
• found in tissue
• same as basophil
• Dark granules
• Histamine, heparin and other enzymes
• Degranulate in response to bound C3b, C3a and antigens
• Cause vasodilation, increased vascular permeability
• Involved in inflammation and allergic responses

Question 7

What are natural killer cells (NK)

Answer 7

Type of white blood cell, which recognize and destroy cancer and virally infected cells

• Innate lymphocyte
• Detects abnormal cells e.g. infected, cancerous or foreign
• Release granules - apoptosis
• Also release IFN-y - anti viral, immune enhancing
• Simple non specific receptors

Question 8

What are eosinophils

Answer 8

white blood cell which is involved in defense against parasitic infection and allergic reactions.

• orange granules
• release toxic proteins
• associated with worm infections, allergy

Question 9

What are basophils

Answer 9

• type of granulocyte
• releases histamine causing vasodilating during allergic reactions - causing swelling, itching and redness in the skin
• promotes inflammation
• allergic reaction
• found in the blood
• same as mast cells

Question 10

What are antimicrobial peptides (defensins)

Answer 10

Proteins that are involved in the innate immune system. They are capable of targeting and killing a variety of microorganisms.

• found on membranes
• 12-50 amino acids in length
• Kill microbes by disrupting cell membrane
• Important on oral mucosa

Question 11

What are lysozymes

Answer 11

enzymes that break down the cell walls of certain bacteria helping to protect the body against infection

• Protein found in secretions (eg. tears, saliva, mucous) and in blood
• Has direct antibacterial actions
• Damages cell walls by breaking peptidoglycan present in cell walls

Question 12

What are dendritic cells

Answer 12

• involved in both innate and adaptive immune system
• function to detect, process and present antigens to T cells,
• antigen presentation to lymphocytes
• Acting as a bridge between innate and adaptive immunity

Question 13

What is phagocytosis

Answer 13

Phagocytosis is the process by which certain cells (known as phagocytes) engulf and digest particles such as pathogens (e.g., bacteria, viruses), dead cells, or other harmful foreign substances. It is a critical part of the innate immune system and is involved in the body’s first line of defense against infections.

Question 14

What is the aim of phagocytosis

Answer 14

to remove extracellular particles ( bacteria, cell debris)

Question 15

Describe the process of phagocytosis

Answer 15

• Cells in blood sense damage in tissues (extravasation)
• Move into tissues and locate are of damage (chemotaxis)
• Cells attach to particle and internalize them forming a phagosome (engulfment)
• Lysosome fuses with phagosome and destroys content of vacuole (digestion/degradation)
• Exocytosis of fragments

Chemotaxis, adherence, ingestion, digestion, killing

Question 16

What cells are able to phagocytose microorganisms

Answer 16

• Macrophages/monocytes
  Neutrophils

Question 17

What is extravastion

Answer 17

• First step in phagocytosis
• process where immune cells (neutrophils, monocytes, macrophage) move from the bloodstream into tissue at the site of infection or injury

Question 18

What are the steps of extravasion

Answer 18

1. Margination
   - leukocytes (white blood cells) move toward the periphery of the blood vessel
2. Adhesion
   - leukocytes bind firmly to the endothelial cells lining
   - mediated by interaction between adhesion molecules on both the leukocytes and endothelial cells
   - this holds the leukocytes in place
   - TNF and IL-1
3. Transmigration
   - where leukocytes squeeze between cells lining the blood vessels)
   - once pass they’re in the tissue where they can move toward the site of infection

Question 19

What is chemotaxis

Answer 19

• step 2 of phagocytosis
  The directed movement of immune cells toward the site of infection, inflammation or tissue damage in response to specific chemicals or cytokines
• When tissues are infector or injured they release chemotactic factors (e.g. cytokines, proteins or bacterial products) these signaling molecules create a concentration gradient in the tissue 9high concentration near the infection site)
• Immune cells like neutrophils or macrophages follow the concentration gradient

Question 20

Which cell arrive to infected tissue first in chemotaxis

Answer 20

• neutrophils
• macrophages arrive later

Question 21

What are the 3 main steps of phagocytosis

Answer 21

1. Adherence
2. Ingestion
3. Digestion

Question 22

What is adherence as first step of phagocytosis

Answer 22

• the binding of the target tot he phagocyte which triggers surface receptors to adhere tightly to the target

Question 23

What is ingestion as the second step to phagocytosis

Answer 23

• once adhesion occurs the phagocyte extends its cell membrane around the pathogen which surrounds and engulfs the pathogen
• This is called a phagosome

Question 24

What is a phagosome

Answer 24

a membrane bound vesicle containing the engulfed pathogen
- what the phagocyte turns into in the second step of phagocytosis (ingestion)

Question 25

What is digestion as the third step in phagocytosis

Answer 25

- the phagosome then fuses with lysosomes (organelles containing digestive enzymes and reactive oxygen species (ROS)) - this fusion forms phagolysosome - The pathogen is exposed to a variety of enzymes which break down and kill the pathogen (e.g. lysozyme, proteases, lipases, ROS)

Question 26

What is a phagolysosome

Answer 26

structure when a phagosome (membrane bounded vesicle containing an ingested pathogen) fuses with a lysosome (organelle filled with digestive enzymes)

Question 27

What is pus

Answer 27

Pus is an accumulation of dead phagocytes, destroyed bacteria, dead cells - formed at the site of inflammation during infection - Caused by purulent (pyogenic) bacteria e.g. actinomyces, staph, e coli

Question 28

What is an abscess

Answer 28

pus accumulating in an enclosed area

Question 29

What is the complement system

Answer 29

- a group of proteins in the blood what enhance the body's ability to fight infections

Question 30

How is the complement system activated

Answer 30

Activated like a set of dominos by - antibody binding to microorganism (classical pathway) - recognition of a surface protein on the microbe - recognition of a surface carbohydrate on the microbe (lectin pathway)

Question 31

What are the 3 main effects of the complement system

Answer 31

1. punctures microbe cell wall/membrane (using MAC) 2. Promotes phagocytosis - opsonisation by C3b or IgG 3. Encourages inflammation - C3a

Question 32

what is opsonisation

Answer 32

process by which pathogens are coated with complement proteins (C3b) to enhance their recognition and uptake by phagocytes. - making phagocytosis easier

Question 33

What is the membrane attack complex (MAC)

Answer 33

- protein structure formed on the surface of pathogen membrane (especially bacteria) that creates a pore or hole in the membrane leading to cell lysis and death - triggered by the 3 complement system - the final step in the complement system

Question 34

What happens if a patient has a deficiency in the complement pathway

Answer 34

reduced immune response

Question 35

When are immune deficiencies suspected

Answer 35

- there is an unusual frequency of infection with common or opportunistic organisms - usually severe infection

Question 36

What are the 2 types of immune deficiencies

Answer 36

- primary (congenital) - secondary (acquired)

Question 37

What are primary immune deficiencies

Answer 37

Immune deficiencies which are genetically inherited Congenital (inherited) - caused by congenital DNA defects affecting the function of leukocytes - Mostly diagnosed before the age of one - >300 primary immuno deficiencies recognized

Question 38

What are dental signs of primary immune deficiencies

Answer 38

- oral candidiasis - gingival enlargement - recurring mouth ulcers, - signs of periodontal disease at a young age - recurring fevers - malaise - recurring bacterial infections (not dental related)

Question 39

What are secondary immune deficiencies

Answer 39

immune deficiencies which are caused by external factors rather than being genetically inherited Acquired examples - chemotherapy - Immunosuppression drugs - HIV - some cancers - chronic disease (diabetes, malnutrition)

Question 40

What are dental signs of secondary immune deficiencies

Answer 40

- periodontal disease (gingival bleeding and swelling) - candidiasis - recurring bacterial infections

Question 41

Disorders of the innate immune system can be due to what

Answer 41

- defects in proteins in complement pathway - can affect activation of pathway or formation of MAC - Defects in phagocyte function - can affect extravasation, chemotaxis, phagosome/lysosome fusion - Defects in natural killer cells - defects in TLR signaling (Toll like receptors) - affects recognition of microbe, activation of signaling pathways

Question 42

What is Leukopenia

Answer 42

- condition of low white blood cells (leukocytes) - making people more susceptible to infections Can be caused by - x-rays, drugs, benzene, chloramphenicol, some barbiturate hypnotics, genetics Causes mouth ulcers

Question 43

What is neutropenia

Answer 43

low count of neutrophil (type of WBC)

Question 44

What is agranulocytosis

Answer 44

severe form of neutropenia where there's the complete absence or extremely low number of all granulocytes (neutrophil, eosinophils, basophil)

Question 45

What is leukemia

Answer 45

Type of cancer what affects the blood and bone marrow, causing uncontrolled growth of abnormal white blood cells (leukocytes), which impairs the body's ability to fight infections, control bleeding and carry oxygen. - proliferative disorder

Question 46

What is myelogenous leukemia

Answer 46

- type of leukemia that affects myeloid stem cells in the bone marrow - affects granulocytes (neutrophils, eosinophils, basophils, mast cell), Macrophage/monocyte erythrocytes, thrombocytes - the bone marrow produces abnormal white blood cells which grow uncontrollably causes - chemotherapy for other cancers, radiation therapy, smoking, down syndrome, genetic disorders Signs and symptoms - fatigue, pallor, weight loss, repeated infections, easy bruising, nose bleeds

Question 47

what are myeloid stem cells

Answer 47

type of stem cell which give rise to various blood cells e.g. - Erythrocytes (RBC) - thrombocytes (platlets) - granulocytes (neutrophls, eosinophils, basophils, mast cells, macrophage/monocyte)

Question 48

What is almost always present in myelogenous leukemia patients

Answer 48

Anemia Because it causes abnormal white blood cells which grown uncontrollably which interferes with the production of normal blood cells. Causing decrease normal blood cells