Immune Response Flashcards
List the 8 stages of the immune response following implantation.
Implantation Blood biomaterial interaction Provisional matrix formation Acute inflammation Chronic inflammation Granulation tissue Foreign body reaction Fibrosis
What are the cells involved in the provisional matrix formation stage?
Fibrin
Activated blood platelets
Inflammatory cells
Endothelial cells
What is acute inflammation?
Leukocytes adsorb to the surface of the biomaterial, resulting in frustrated phagocytosis.
What are the cells involved in the acute inflammatory stage?
Neutrophils (initially)
Macrophages (later)
What is the chronic inflammation stage?
Characterised by the presence of macrophages, monocytes and lymphocytes, with the proliferation of blood vessels and connective tissue
What are the cells involved in the chronic inflammatory stage?
Macrophages
Monocytes
Lymphocytes
What happens in the granulation tissue stage?
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.
What cells are involved in the granulation tissue stage?
Fibroblasts
Macrophages
Endothelial cells
Collagen/proteoglycans
What is the foreign body reaction?
Fused macrophages form a FBGC
What are the cells involved in the foreign body reaction phase?
Macrophages
What is fibrosis?
Fibroblasts create a capsule of connective tissue that wraps up the implant and isolates it from the surrounding connective tissue
What are the cells involved in fibrosis?
Fibroblasts
What is frustrated phagocytosis?
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.
What is the purpose of inflammation?
To contain, neutralise, or wall off the injurious agent, setting off the regenerative process.
What does it mean if a biomaterial gets to the fibrosis stage?
It is bioinert & biocompatible
What biomaterials does a fibrous capsule not form for?
Porous materials - infused with connective tissue
Nonporous bioactive materials - normal connective tissue interfaces with them
Biodegradable materials - metabolised away
Toxic materials - ongoing cell death
How do you minimise fibrous capsule formation?
More bioinert material
Less movement between implant and tissue
No toxin leaching
Eliminate entirely by using bioactive materials
What is an autograft? Name one advantage and two disadvantages.
Bone graft harvested from the same person.
Advantage:
- Identical genetic makeup = no immune response
Disadvantage:
- Limited availability
- Donor site morbidity
What is an allograft? What is the central balancing act involved?
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.
What are xenografts?
Bone grafts taken from another species.
What is adsorption?
The adhesion of elements to a surface.
Name 4 rules of protein adsorption.
- A biofluid contains many proteins, which adsorb to the material surface within seconds.
- Adsorption of various proteins is competitive with one another
- The higher the conc of a protein the higher the adsorption (INITIAL)
- The higher the affinity of a protein to the surface, the higher the adsorption (EQUILIBRIUM)
What is the Vroman effect?
Initial - higher concentration of proteins in surrounding fluid with adsorb to surface
Equilibrium - higher affinity proteins will adsorb more
What is a neutrophil?
A white blood cell formed in bone marrow that self destruct after destroying a pathogen.
