Day 3- Lecture 1- Chronic Inflammation Flashcards
What is chronic inflammation?
Chronic response to injury with associated fibrosis (longer, more variable, overlap with host immunity)
With regards to the 4 clinical signs on acute inflammation which 2 resolve and which 2 persist?
- Redness and heat resolve
- Swelling and pain persist
When does acute inflammation occur?
Seconds to minutes after injury - instant reaction to any type of injury
What is the purpose of acute inflammation?
To phagocytose bacteria, with or without the help of plasma proteins, before they can establish a secured position
How long does it take for modulated chronic inflammation to replace acute inflammation?
It takes over in a few hours if the injurious agent is not quickly removed
What is the dominant cell type of modulated (chronic) inflammation?
Macrophages
Give some examples of the possible persisting injurious agents in chronic inflammation?
- Micro-organism e.g. Bacteria
- A sterile but irritating substance such as necrotic tissue
- A foreign body
- A crystalline substances
- An antigen (e.g. In autoimmune disease)
How does chronic inflammation arise?
1- When it takes over from acute inflammation (most common) - if damage is too severe to be resolved within a few days
2- When it begins without any proceeding acute inflammation (de-novo)
3- When it develops alongside an superimposed on acute inflammation (repeated attacks of acute inflammation can lead to it developing alongside it)
Give some examples of when chronic inflammation may arise without any proceeding acute inflammation?
- Some chronic infections e.g. TB
- Some autoimmune conditions e.g. Rheumatoid arthritis
- Prolonged exposure to toxic agents e.g. Silica
What does chronic inflammation look like under a microscope?
Much more varied than acute inflammation- look for presence of cell types (look at my notes)
Give an example of when chronic inflammation develops alongside acute inflammation?
In an on-going bacterial infection
What does chronic inflammation look like under a microscope?
- Mononuclear cells- macrophages and lymphocytes- are the predominant cell type
- A new type of tissue called granulation tissue begins to form-> part of the healing process
Tip: the shift from neutrophils to macrophages and lymphocytes indicates that they have different functions- macrophages and lymphocytes are always seen in chronic inflammation but the numbers seen and mix present varies considerably
What cells are principally involved in chronic inflammation, and what are they general role?
Macrophages- phagocytosis, presentation of antigens to immune system, synthesis of important proteins and enzymes, control of other cells
Lymphocytes- B type (plasma cells) produce antibodies, T type involved in control and cytotoxic functions
Eosinophils- allergic reactions, parasite infections
Fibroblasts/myofibroblasts- make collagen
What are macrophages called before they enter the tissue?
Monocytes
What is another name for macrophages (in tissue spaces)?
Histiocytes
Where are monocytes made?
Bone marrow
How long do monocytes circulate in the blood for and what happens after this time period?
About 6 days - they then enter the tissues and become dormant until activated by a local challenge
How long do macrophages last for?
Many months- and they can replicate (unlike neutrophils)
Where do macrophages go and what do they initially do?
The arrive at the site of inflammation after the neutrophils and take over from them
List and explain the 6 functions of macrophages?
- Phagocytosis and destruction of debris (e.g. Dead tissue and collagen) and bacteria- not always as effective as neutrophils, however better at destroying some difficult to kill bacteria e.g. Mycobacterium tuberculosis
- Secretion of numerous substance that summon and activate other cells (e.g. Cytokines, complement components, blood clotting factors, proteases)
- Present antigens to the immune system and initiate an immune response
- Stimulates angiogenesis (the formation of new blood vessels) which is important in wound healing
- Induces fibrosis
- Induces fever, acute phase reaction and chachexia
What are the predominant cells of the immune system?
Lymphocytes
What are plasma cells?
Differentiate antibody-producing B lymphocytes (produce, synthesise and secrete antibodies). Usually implies considerable chronicity. As differentiated, takes time, so if present, tells you inflammation has been going on for a while.
Lymphocytes are normally absent in the tissues, if they are present what does it indicate?
That some antigenic material is or has been there
What do lymphocytes do?
- Process antigens
- Secrete antibodies (this is done by B lymphocytes that have undergone differentiation to become plasma cells which secrete antibodies)
- T lymphocytes: Secreting cytokines that influence other inflammatory cells
- T lymphocytes: Killing cells (this is done by natural killer cells which attack virus-infected cells and sometimes tumour cells)
B lymphocytes- produced and mature in bone marrow
T lymphocytes- produced in bone marrow and mature in thymus