Week 11 Flashcards
What Are Dendritic cells?
A special type of immune cell that is found in tissues, such as the skin, and boosts immune responses by showing antigens on its surface to other cells of the immune system
What do the distinctions between human and murine dendritic cells reflect?
Differences in tissue origin and differences between cultured and freshly isolated DCs
How are different subsets of human and mouse dendritic cells separated?
On the basis of surface antigen differences
What are the different distinctions between dendritic cell subtypes?
Respond differently to microbial products, produce different cytokines and regulate the responses of the T cells they activate
What are the dendritic cell subtypes products of?
Separate developmental sublineages with different immediate precursors
What do some dendritic cells only produce?
DCs from pDCs in response to microbial products or other danger signals
When do dendritic cell subtypes exit their mature, quiescent state?
When activated by microbial products or other danger signals
What determines the balance between tolerance and immunity?
The dynamics of these shifts in the DC system in response to microbial invasion
What are conventional dendritic cells?
Innate immune cells
What does the term cDC refer to?
All DCs other than plasmacytoid DCs
Where do conventional dendritic cells reside?
In tissues and, following tissue infection or injury, they become activated and migrate to draining lymph nodes to promote adaptive immune responses
What are plasmacytoid dendritic cells?
A unique subset of dendritic cells specialised in secreting high levels of type I interferons
What is the function of active pDC?
Link innate immunity and adaptive immunity to viruses
What is the role of dendritic cells in the innate immune system?
As a component of the innate immune system, DC organize and transfer information from the outside world to the cells of the adaptive immune system
What are the three distinct signals of primary T cell activation?
(1) anti- gen recognition
(2) costimulation
(3) cytokine- mediated differentiation and expansion
What occurs during dendritic cell maturation?
During maturation, the DCs begin to synthesize peptides that include major histocompatibility complex (MHC) II molecules, CD40, CD80, and CD86 costimulatory molecules and proteins like CD83 and DC-LAMP that have little known functions
What does antigen recognition by B cells involve?
Direct binding of immunoglobulin to the intact antigen and antibodies typically bind to the surface of protein antigens, contacting amino acids that are discontinuous in the primary structure but are brought together in the folded protein
What do you mean by co stimulation?
Co-stimulation is a secondary signal which immune cells rely on to activate an immune response in the presence of an antigen-presenting cell
Which are pattern recognition receptors?
Pattern Recognition Receptors (PRRs) are proteins capable of recognizing molecules frequently found in pathogens (the so-called Pathogen-Associated Molecular Patterns—PAMPs), or molecules released by damaged cells (the Damage-Associated Molecular Patterns—DAMPs)
What are the three major dendritic cell subsets?
Plasmacytoid DC (pDC), myeloid/conventional DC1 (cDC1) and myeloid/conventional DC2 (cDC2)
How do pattern recognition receptors emerge?
They emerged phylogenetically prior to the appearance of the adaptive immunity and, therefore, are considered part of the innate immune system
What do the signals from the pattern recognition receptors activate?
Microbicidal and pro-inflammatory responses required to eliminate or, at least, to contain infectious agents
How does the innate immune system detect viruses?
Through molecular sensors that trigger the production of type I interferons (IFN-I) and inflammatory cytokines
Why are multiple sensors needed to detect viruses?
Because viruses vary tremendously in size, structure, genomic composition, and tissue tropism
What are the similarities between type I and type III IFN signalling?
Type III IFNs, like type I, are induced upon PRR recognition of PAMPs and signal through the shared JAK-STAT pathway to induce a similar antiviral transcriptional program
What are IFNs?
Secreted cytokines that activate a signal transduction cascade leading to the induction of hundreds of interferon-stimulated genes
What are type I interferons?
Polypeptides that are secreted by infected cells and have three major functions