Immune Response

Question 1

List the 8 stages of the immune response following implantation.

Answer 1

Implantation
Blood biomaterial interaction
Provisional matrix formation
Acute inflammation
Chronic inflammation
Granulation tissue
Foreign body reaction
Fibrosis

Question 2

What are the cells involved in the provisional matrix formation stage?

Answer 2

Fibrin
Activated blood platelets
Inflammatory cells
Endothelial cells

Question 3

What is acute inflammation?

Answer 3

Leukocytes adsorb to the surface of the biomaterial, resulting in frustrated phagocytosis.

Question 4

What are the cells involved in the acute inflammatory stage?

Answer 4

Neutrophils (initially)

Macrophages (later)

Question 5

What is the chronic inflammation stage?

Answer 5

Characterised by the presence of macrophages, monocytes and lymphocytes, with the proliferation of blood vessels and connective tissue

Question 6

What are the cells involved in the chronic inflammatory stage?

Answer 6

Macrophages
Monocytes
Lymphocytes

Question 7

What happens in the granulation tissue stage?

Answer 7

Fibroblasts and endothelial cells arrive and begin to form granulation tissue (soft, pink tissue characteristic of the healing process)

Fibroblasts actively synthesise collagen and proteoglycans (ECM), while endothelial cells work to proliferate small blood vessels.

Question 8

What cells are involved in the granulation tissue stage?

Answer 8

Fibroblasts
Macrophages
Endothelial cells
Collagen/proteoglycans

Question 9

What is the foreign body reaction?

Answer 9

Fused macrophages form a FBGC

Question 10

What are the cells involved in the foreign body reaction phase?

Answer 10

Macrophages

Question 11

What is fibrosis?

Answer 11

Fibroblasts create a capsule of connective tissue that wraps up the implant and isolates it from the surrounding connective tissue

Question 12

What are the cells involved in fibrosis?

Answer 12

Fibroblasts

Question 13

What is frustrated phagocytosis?

Answer 13

In general, phagocytes aim to destroy pathogens by engulfing them and subjecting them to a battery of toxic chemicals. If a phagocyte fails to engulf its target, these toxic agents can be released into the environment (FRUSTRATED PHAGOCYTOSIS). As these agents are also toxic to host cells, they can cause extensive damage to healthy cells and tissues.

Question 14

What is the purpose of inflammation?

Answer 14

To contain, neutralise, or wall off the injurious agent, setting off the regenerative process.

Question 15

What does it mean if a biomaterial gets to the fibrosis stage?

Answer 15

It is bioinert & biocompatible

Question 16

What biomaterials does a fibrous capsule not form for?

Answer 16

Porous materials - infused with connective tissue
Nonporous bioactive materials - normal connective tissue interfaces with them
Biodegradable materials - metabolised away
Toxic materials - ongoing cell death

Question 17

How do you minimise fibrous capsule formation?

Answer 17

More bioinert material
Less movement between implant and tissue
No toxin leaching

Eliminate entirely by using bioactive materials

Question 18

What is an autograft? Name one advantage and two disadvantages.

Answer 18

Bone graft harvested from the same person.

Advantage:
- Identical genetic makeup = no immune response

Disadvantage:

• Limited availability
• Donor site morbidity

Question 19

What is an allograft? What is the central balancing act involved?

Answer 19

Bone graft harvested from the same person.

The processing chemicals and irradiation used significantly reduces the mechanical integrity of the graft, and impedes the tissue’s osteoconductive potential. Hence, a compromise between biological safety and mechanical integrity is the main limitation of allografts.

Question 20

What are xenografts?

Answer 20

Bone grafts taken from another species.

Question 21

What is adsorption?

Answer 21

The adhesion of elements to a surface.

Question 22

Name 4 rules of protein adsorption.

Answer 22

1. A biofluid contains many proteins, which adsorb to the material surface within seconds.
2. Adsorption of various proteins is competitive with one another
3. The higher the conc of a protein the higher the adsorption (INITIAL)
4. The higher the affinity of a protein to the surface, the higher the adsorption (EQUILIBRIUM)

Question 23

What is the Vroman effect?

Answer 23

Initial - higher concentration of proteins in surrounding fluid with adsorb to surface
Equilibrium - higher affinity proteins will adsorb more

Question 24

What is a neutrophil?

Answer 24

A white blood cell formed in bone marrow that self destruct after destroying a pathogen.

Question 25

What is a macrophage?

Answer 25

Type of white blood cell that engulfs and digests pathogens - derived from monocytic white blood cells

Question 26

What are the key differences between innate and adaptive immune responses?

Answer 26

Innate - non-specific

Adaptive - specific response, systemic response (throughout whole body), has a memory.

Question 27

What are the two defenses that make up the adaptive immune response?

Answer 27

Humoral response - antibodies & B cells

Cellular defence - t cells

Question 28

What is an antigen?

Answer 28

A small amino acid chain that stimulates an immune response - signalling molecules not normally found in the body.

Question 29

What is a pathogen?

Answer 29

A bacterium, virus, or other microorganism that can cause disease

Question 30

What is an antibody?

Answer 30

A blood protein produced in response to specific antigens

Question 31

What is the key difference between B and T cells?

Answer 31

B cells - attack outside cell

T cells - attack inside cell