IAI - WS: IAI - Immunology Flashcards
What are the differences between innate and adaptive immunity?
Innate:
- faster
- doesn’t have memory (in general)
- non-specific
Adaptive:
- slower
- does have memory
- specific
Describe the mechanism that generates a diverse array of B and T cell receptor specificities, that is common to B and T cells.
Gene rearrangement of V, D and J segments.
It is done by RAG genes, and involves rules such as the 12-23 rule, to ensure you add the gene segments in the right order.
There are also random nucleotides added in to increase the variety further.
Compare the ways in which dendritic cells, B cells and T cells recognize foreign antigens.
Dendritic cells:
TLRs receptors on their surface that bind to PAMPs/DAMPs.
B Cells:
They have BCRs on their surface, which are essentially immunoglobulins that recognise specific antigens.
T Cells:
They have TLRs, which only recognize peptides presented on the MHCs to the T cell. It also needs to bind to a second signal of co-receptors.
Describe the structure of immunoglobulins/ antibodies discriminating between the regions that recognize specific antigen and regions involved in mediating effector function.
There are variable and constant regions. The variable regions can recognize specific antigens, whilst the constant regions maintain the effector function of the antibody.
What are the functions of immunoglobulin/ antibody?
- Neutralise toxins and viruses by binding to them and blocking their interaction with other cells
- Opsonise pathogens by binding to them to promote phagocytosis and killing activity by other cells by recognition of Fc receptors
- Activate the complement cascade which helps kill pathogens
- Agglutinates particles (pathogen debris, viruses etc)
Why are antibody responses to second and subsequent immunizations faster and of better quality than the first (primary) immunization?
After the initial infection, there are long-term memory cells that remain, such as plasma cells, which allow for a faster secondary response.
You essentially have a higher frequency of memory T and B cells for that specific antigen.
What are CD4 and CD8?
They are co-receptors found on T cells, which help stablise the reaction between MHCI for CD8 and MHC II for CD4.
What is the difference between CD4 and CD8 recognition of antigen?
Intracellular pathogen antigens are processed internally, then presented on MHC I to CD8.
Exogenous pathogens, such as bacteria, processed and presented on MHC II to CD4.
In terms of T cell selection in the thymus, what is the difference between, and importance of, positive and negative selection?
Positive: important for T cells to recognize your own MHC, and become either CD4 or CD8 (not both).
Negative: ensure that they do not recognize or bind too strongly to self-antigens, to avoid inducing auto immunity.
In the context of CD4 T cells, what do the following terms describe:
- Naïve
- Memory
- Effector
Naïve: a T or B cell that has not met its antigen yet
Memory: a circulating T or B cell (at higher frequencies than other cells) that is prepped for a specific antigen, and ready to launch an increased secondary response
Effector: a T or B cell that has been activated, and having an effect (making cytokines, killing things through release of granzymes)
What are the 4 main types of T effector cells, and what specific effects do they have?
Th1: mainly involved against viruses and other intracellular pathogens – characterized by making IFN-gamma, to activate macrophages against infection
Th2: provide help for B cells, and promote clearance of parasites via activation of eosinophils (also used in allergy) – they secrete IL-4, IL-5 and IL-13
Th17: fight extracellular bacteria and fungi – they secrete IL-17, IL-21 and IL-22 – particularly found in the gut, to maintain healthy mucosa environment
Treg: they help downregulate immune responses – they secrete TGF-beta and IL-10, important transcription factor is Foxp3 (when people lack this, they develop autoimmune condition APCED that affects many body organs)
