6. Adaptive immune response Flashcards
What are naive T cells?
T cells that has not encountered an antigen
Which cell is required for naive T cells to be activated?
Antigen presenting cells. These APCs: Sense the pathogen Capture the pathogen Process the pathogen Present their antigens on their surface. The naive T cells will bind to the APCs and will be activated
Differentiate between naive T cells and effector T cells
Naïve T cells = T cells that have not previously encountered the antigen
Effector T cells = T cells that have previously encountered the antigen and are capable of performing effector functions during an immune response
List the 4 main types of APCs and provide the type of cell they provide the pathogen to as well as the function of the activated T cell
- Dendritic cells
They present the pathogen to naive T cells.
The T cell mounts a response against most pathogens. - Langerhans cells
They present the pathogen to naive T cells.
The T cell mounts a response against most pathogens. - Macrophages
They present the pathogen to effector T cells.
The T cells are used to stimulate and increase the activity of phagocytes in destroying pathogens. - B cells
They present the pathogen to effector T cells.
The T cells are used to stimulate and increase the antibody response (humoral response).
Give the 3 main features of APCs
- These APCs have strategic positioning within the body and can be found at every portal of entry.
E.g
o Mucosal membranes(MALT) (gut(GALT), lung)(NALT, BALT, GUALT)
o Skin (i.e., Langerhans cells) (SALT)
o Blood (i.e., plasmacytoid cells)
o Lymph nodes (i.e., follicular dendritic cells)
o Spleen - There’s diversity when it comes to the pathogen sensors (PRRs) found in these APCs.
There’ll be different types of PRRs for extracellular as well as intracellular pathogens(virus). - There’s diversity in the mechanisms used to capture pathogens.
E.g phagocytosis in order to capture the whole microbe whilst macropinocytosis is used to capture soluble particles.
Best type of PRR? Why is it important?
Toll like receptor
Over activation of TLR4 in sepsis leading to organ failure.
Why are antigen presenting cells important?
Only way to activate T cells to stimulate immune response.
Tells T cell that’s there’s an invader
What the invader looks like
What response T cell needs to do
Why do we struggle to ID cancer?
Some cancers can emit signals that can suppress immune system.
Describe the steps taken when a pathogen enters the body
- There’s a breach in the innate barriers somewhere in the body allowing the pathogen to enter the body.
- Macrophages of the innate immunity start triggering the innate immune process.
- If the microbe gets into the blood it’ll end up reaching the spleen where’ll it be captured.
- Antigen presenting cells will pick up the pathogens in tissue and use the lymphatics to capture it.
They’ll then take it to the nearest lymphoid tissue (e.g the BALT) where there’s an abundance of adaptive immune cells. - The pathogen is processed and there’s the expression of microbial antigens on APCs.
- The microbial antigen is then presented to the right T cells.
What is an HLA system?
The human leukocyte antigen (HLA) system or complex is a gene complex that codes for the major histocompatibility complex (MHC) proteins in humans.
HLA genes are highly polymorphic, which means that they have many different alleles, allowing them to fine-tune the adaptive immune system.
How are pathogens presented on the surface of an APC, differentiate between the 2 molecules involved
Pathogens are presented by Major Histocompatibility Complex (MHC) molecules.
There are 2 types:
- The MHC class 2 molecules
- MHC class 1 molecules
Where are antigen presenting cells found?
o Mucosa associated lymphoid tissue (MALT)
- Skin (SALT)
- Mucous membranes (GALT, NALT, BALT, GUALT)
- Tonsils or Peyer’s patches
o Lymphoid organs (Lymph nodes, spleen)
o Blood circulation
What are antigen presenting cells in blood circulation called?
plasmacytoid and myeloid DCs
What are the main TLR for identifying gram positive and gram negative bacteria?
Positive: TLR2
Negative: TLR4
Which TLR recognises adenovirus?
TLR9
