The adaptive immune cells to “remember” which pathogens have been seen before. Protects against subsequent infections.
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Follicular dendritic cells
Cells of the immune system found in primary and secondary lymph follicles of the B cell areas of the lymphoid tissue.
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Memory B cells
Antibody can persist for many years after vaccination / infection. Memory B cells (MBC) and long lived plasma cells (LLPC) Memory B cells live primarily in the secondary lymphoid tissues. Long-lived plasma cells live in the bone marrow.
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Transcription factors involved in B cell memory differentiation
PAX-5, MITF, Blimp-1, XBP-1 and IRF-4
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B cells
High affinity BCR, proliferate rapidly in response to antigen. MBCs up-regulate antibody production upon activation.
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Plasma cells
No BCR on their surface, cannot be stimulated to divide. constitutively produce antibody.
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Class switched
Ensuring that secondary response to pathogen is rapid. Don’t have IgM or IgD on surface.
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Central memory T cells (TCM)
Expression of the cell adhesion molecule CD62 Ligand and the chemokine receptor CCR7. effector functions in the absence of antigen. TCM cells proliferate madly in response to antigen.
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Effector memory T cells (TEM)
TEM are identified by down-regulation of the cell adhesion molecule CD62 Ligand and the chemokine receptor CCR7. respond to antigen when present and live in peripheral tissues as well as lymphoid organs. TEM proliferate less than TCM.
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Divergent pathway (T and B cells)
Activated cells branch depending on antigen dose or inflammatory stimuli.
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Activation signals
Memory T cells can assimilate TCR signals (signal 1) better than naïve T cells.
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Clonal expansion
Memory T cells are precharged with factors allowing G1-S phase in the cell cycle (fast proliferation) .
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Location
Naïve T cells are largely located in the lymphoid organs whereas TEM are also present in non-lymphoid tissue and mucosal sites.
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Gene expression in memory T cells is already pre-programmed
Memory T cells behave in a manner similar to their parent cell eg. a parental Th1 will divide to give rise to memory Th1. Gene expression profiles are altered by epigenetic changes.
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Epigenetic changes
DNA methylation, Histone modifications, reorganisation of chromatin structure.
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Naive T Cell activation
1 signal (TCR/MHC:peptide). Signal 2 (co-stimulation) = t cell activation
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Memory T Cell activation
1 signal (TCR/MHC:peptide) = activation of effector functions. No requirement for co-stimulation.
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Survival Cytokines For Memory T Cells
IL-7 & IL-15.
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Receipt of survival signals by memory T cells
T cells signal received via the IL7 receptor and the IL-15 receptor activate Bcl-2. Bcl-2 prevents Bim from activating the pro-apoptotic factors Bak and Bax. Signalling via the IL-7 receptor occurs via the STAT 5.
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Memory T cells survive by preventing apoptosis
Il-7 and IL-15 act as survival factors by preventing apoptosis. If neither IL-7 nor IL-15 are present then the cell will die as Bcl-2 will not be transcribed. In the absence of IL-7 and IL-15 T cells will undergo apoptosis via Bak and Bax activation
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Other cards in this set
Card 2
Front
Follicular dendritic cells
Back
Cells of the immune system found in primary and secondary lymph follicles of the B cell areas of the lymphoid tissue.
Card 3
Front
Memory B cells
Back
Card 4
Front
Transcription factors involved in B cell memory differentiation
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