Adaptive Immunity Flashcards
how long can the adaptive immune response take to activate
days - weeks
what is the first thing lymphocytes do after antigen binding
enter the cell division cycle to divide by mitosis and expand their population
which two types of cells do lymphocytes differentiate into after clonal expansion
memory cells
effector cells
what two major zones are lymph nodes organised into
B cell follicles around the edges
T cell zone in the middle
where do B cells get activated by antigens
lymph nodes
which chemokine helps with the expression of co-stimulatory molecules when dendritic cells are displaying MHC-peptide complexes
TNF alpha
explain how high endothelial venules allow lymphocytes to escape blood vessels and enter the lymph system
they constitutively express all of the necessary adhesion molecules to attach to the lymphocytes allowing transepithelial migration
(similar to how neutrophils enter infected tissues)
what do accessory molecules do
stabilise the interaction of APCs and TCRs and provide co-stimulation
what type of cells are in the B cell zone of lymph nodes
stromal cells that can be enriched for the expression of opsonin receptors
explain T cell-independent B cell activation
long chain carbohydrate binds
BCR clustering
not as efficient as T cell dependant
can only produce IgM - low/medium affinity
memory cells not created
smaller amounts of IL-2
explain T cell-dependant B cell activation
TCR binds MHC II along with co-stimulatory molecule binding
large amounts of IL-2
what does the differentiation of lymphocytes depend on
cytokine environment
what epitopes can T-cells respond to
only peptides
what epitopes can B-cells respond to
anything
what two things related to IL-2 do activated T-cells do
upregulates the transcription and translation of IL-2
increases the expression of the high-affinity subunits of the IL-2 receptor
what does IL-2 binding lead to
entry into the cell cycle and clonal expansion
what is the primary source of IL-2
activated CD4 T cells
what is the T-helper nought state
T helper cells are activated and have proliferated but not yet fully differentiated
what dictates the cytokine environment
the pathogen causing the response
what are CD4 TH4 cells
effector T helper cells which secrete IFN gamma which favours macrophage activation and cell-mediated responses
what are CD4 TFH (T follicular helper cells)
effector T helper cells which secrete IL-21 which stimulates B cell activation within the lymph node
what is the role of TH1 cells?
effector T helper cells which use co-stimulation to hyperactivity macrophages, enhancing their activity (killing, TNF alpha secretion)
what are the primary targets of cytotoxic T cells?
virally infected cells
cells infected with intracellular pathogens
explain the cytotoxic T-cell granule-killing mechanisms
they contain granules full of toxic proapoptotic-inducing factors
the contents of these granules are released into the target cell via a narrow cleft (prevent killing of surrounding healthy cells)
why is T cell activation switched off during a prolonged infection?
limit bystander tissue damage
