Defence Cells Flashcards
What is immune dysregulation?
When the immune system is not functioning normally (impairment of the immune system)
Where do nearly all defence cells originate?
In the bone marrow
What are haematopoietic cells?
Cells that can differentiate into any type of blood cell: RBC, WBC or platelet
Where do lymphoid cells originate?
In the lymph glands
Where do myeloid cells originate?
In the bone marrow
What are common myeloid precursors?
- Macrophages
- Neutrophils
- Mast cells
- Basophils
- Eosinophils
- RBC
What are common lymphoid precursors?
- B cells
- T cells
Are neutrophils granulocytes?
Yes, they have secretory granules in them
- these contain degradative enzymes and antimicrobial substances within them
Which cells are the most numerous and important cells in innate immune responses?
Neutrophils
Where are neutrophils found in the body?
- They circulate in the blood and move into tissues when requires
- Healthy people will have millions of neutrophils in the body
What is meant by neutrophils being phagocytic?
They take up and destroy organisms by phagocytosis
What is chemotaxis?
The movement of an organism in response to a chemical stimulus
Which cells circulate in the blood as precursors called monocytes?
Macrophages - they become macrophages once they migrate into the tissue
Are macrophages early responders to infection or tissue damage?
Yes, they are long lived with multiple functions
What is it meant by macrophages being ‘antigen presenting cells’?
They are able to phagocytose but can also present antigens to other cells
Are mast cells granulocytes?
Yes, they are best known for their role in allergy as they produce histamine
Are mast cells early responders to infection or tissue damage?
Yes, they migrate from blood and differentiate into tissues
What to mast cells protect against?
Pathogens - particularly larger pathogens e.g. parasitic worms
Are Eosinophils granulocytes?
Yes, they contain degradative enzymes and antimicrobials
Do eosinophils contribute to allergy?
yes
Why are eosinophils thought to play a major role in defence against parasites?
Because they are larger than neutrophils so can ingest larger threats
Are basophils granulocytes?
Yes
What cells are basophils similar to?
Eosinophils
Where are dendritic cells derived from?
Both myeloid and lymphoid lineages
What is the function of dendritic cells?
Can uptake antigens and can also present antigens to T cells or sometimes directly to B cells
What do dendritic cells look like?
Long, finger-like processes
What is micropinocytosis?
The ability of dendritic cells to ingest large amounts of extracellular fluid
Where do T cells mature?
The Thymus
What do T cells give rise to?
Cellular immunity
How do T cells recognise peptides presented by antigen presenting cells?
Through T cell receptors
Why are there checkpoints in place for T cells?
To ensure T cells only respond to foreign pathogens and not ‘self peptides’
What 2 sub-groups can T cells be classified into?
CD8+ or CD4+
What do CD8+ T cells interact with?
Antigen presented by MHC class 1 (can be suicidal gene)
What do CD4+ T cells interact with?
Antigen presented by MHC class 2 (signal to show that needs response to remove threat)
What do cytotoxic CD8+ T cells do?
Destroy infected ‘self cells’
What do CD4+ cells play a role in?
Immune detection. Numerous subsets which help support and modulate immune responses according to pathogenic threat. Also roles in regulation of immune responses
What is the cytotoxic process of CD8+ T cells?
- when a cytotoxic T cell interacts with the MHC 1-epitope complex on an infected cell it produces granzymes and perforins
- The perforins form pores in the plasma membrane. Granzymes enter the cell and break down proteins, lysing the cell
What is the CD4+ T cell subset generation process?
- CD4+ T cells start life as a ‘naive’ T cell
- 3 signals are requires for the activation of T cells
- 3rd Signal determines the fate f the naïve T cell
What is the function of TH1 CD4+ T cells?
Support macrophages to destroy intracellular microbes
What is the function of TH2 CD4+ T cells?
Produce cytokines which recruit and activate mast cells, eosinophils and promote barrier immunity at mucosal surfaces
What is the function of TH17 CD4+ T cells?
Secrete IL-17 family cytokines that induce local non-professional immune cells to release cytokines and chemokines
What is the function of TFH CD4+ T cells?
Cells induce specific B cell responses (promote opsonising antibody response)
What is the function of Treg CD4+ T cells?
Supress T cell activity to prevent autoimmunity
How do B cells recognise antigens?
Through B cell receptors which is the actual antibody against the antigen they respond
What is meant by ‘diversity’ in B cell receptors?
Potential to respond to numerous antigens
Once activated what do B cells turn into?
Plasma cells which churn out lots of antibody against that specific antigen
What can binding of the antigen to the B cell receptor lead to?
Internalisation and subsequent antigen presentation to T cells
Why are checkpoints in place for B cells?
To ensure B cells only respond to foreign pathogens and not ‘self-peptides’
What are the 3 major functions of B cells?
- Proliferation - Multiply in numbers
- Antigen presentation - to activate T cells
- Plasma cell differentiation - Produces antibodies
Which myeloid cells are considered part of innate immunity?
Natural killer cells
Do NK cells have granules?
Yes
Which abnormal cells can NK cells recognise and kill?
- Tumour
- Infected virus
Why are Natural Killer cells important?
They can ‘hold back’ virus infections until adaptive immunity kicks in
