Cells of the immune system? Flashcards
what drives cellular differentiation?
cytokines
- differentiation is also driven by the location of the stem cells
what are the features of immature T and B cells?
found in the bone marrow
- the TCR/BCR genes are still in the germline state
what is gene rearrangement of TCR/BCR genes?
DNA based mechanism that loops out genes, creating a new and unique DNA sequence
what part of antibody genes are rearranged?
the heavy and light chains
what part of T cell receptors undergo rearrangement?
Alpha and beta chains
what is clonal expansion?
selective expansion of lymphocytes that interact with antigen
what happens when B cells undergo clonal expansion?
the daughter cells produce antibody specific for the interacting antigen
what can help determine an adaptive immune system?
immunization
how do neutrophils respond during an infection?
they expand in response to infection
what are the features of neutrophils?
-produced in the bone marrow
- most abundnat leukocyte but short-lived
-dead and dying neutrophils are a mjor component of pus
-Produced reactive oxygen species (ROS) and NETS
what is the function of neutrophils producing reactive oxygen species?
they are used to kill microbes
what are NETS?
DNA and histones that are released by a dying neutrophil
why do neutrophils breakdown?
production of reactive oxygen species effects the ingegrity of the cell wall and othe essential parts of the cellular structure and so the neurophil dies
what is the function of NETS?
Neutrophil Extracellular Traps bind bacteria
what is the primary function of dendritic cells?
to excite the immune system
what are the features of dendritic cells?
-Antigen-presenting cells that can activate naive T cells
-Express both MHC-I and MHC-II and costimulatory molecules
- Migratory function (ferry antigen from the periphery to the lymph node)
-all solid organs and blood contain dendritic cells
what cell is responsible for acute transplant rejection?
dendritic cells
what are the dendritic cell subsets derived from?
common myeloid progenitor cells
what are the subsets of dendritic cells?
- Langerhans cells
- Dermal dendritic cells
- Thymic dendritic cells
what are langerhans cells?
dendritic cells of the epidermis
what are dermal dendritic cells?
cells specialised in cross-priming
what is the role of thymic dendritic cells?
medial central tolerance
what is central tolerance?
deletion of autoreactive T cells
what allows cross priming?
the phagolysosome leaking into the cytoplasm
what is exogenous processing?
outside ‘stuff’ gets loaded onto MHC-II
what is endogenous processing?
inside ‘stuff’ gets loaded onto MHC-I
what does MHC-II activate?
Helper T cells (CD4)
what does MHC-I activate?
Cytotoxic T cells (CD8)
what is the role of conventional dendritic cells?
Main subset involved in stimulating naive and memory T cells
what is the role of plasmacytoid dendritic cells?
release large amounts of interferon type 1
what is the role of interferon type 1?
puts the body into a state of high alert
what is the role of peripheral tolerance?
keeps autoreactive immunes cells at bay
what happens to immune cells that show a lack of co-stimulation?
lack of co-stimulation leads to anergy (non-responsiveness) or cell death
what is the result of a cell undergoing co-stimulation?
leads to lymphocyte activation
what are the features of macrophages?
- monocyte in the blood is a macrophage precursor
- role in antigen clearance
- monocytes can activate coagulation through upregulation of clotting factors
how is macrophage activation enhanced by the immune system?
presentaion of intracellular antigens by macrophages leads to interactions with CD4 T cells
CD4 T Cells then release INFg which activates anti-bacteria activity in macrophages
what is the role of a natural killer cell?
Recognise inhibitory receptors on normal cells (MHC-I)
If MHC-I is missing or altered, Natural killer cells become activated and lyse the target cell
why does lack of MHC-I activate a natural killer cell?
build up of a positive signal to lyse the cell, which is inhibited by the presence of MHC-I, is not inhibited due to MHC-I not being present
what are Natural Killer cells?
NK cells are primarily an innate cell, but are essential for the development of tumour immunity
NK cells infiltrate lymph nodes and contribute to T cell activation
how to natural killer cells help with cancer?
Caner and viruses interfer with the expression of MHC-I on the cell surface which can cause the NK cell to become activated
what receptors are important for triggering macrophages and NK cells?
Fc receptors
- recognises the fc region of an antibody
how do natural killer cells kill host cells via antibody-dependent cellular cytotoxicity?
- Antibodies bind antigens on the surface of target cells
- NK cell CD16 Fc receptors recognise cell-bound antibodies
- Cross-linking of CD16 triggers degranulation into a lytic synapse
- Tumour cells die by apoptosis
what is a hot tumour?
high mutational burden
why is a tumor with more mutations easier to generate a T cell response to?
There is a greater variety of peptides specific to the tumor that the T cells can recognise
