Immunological memory Flashcards
where are short-lived plasma cells located?
They reside in the lymph node or spleen
where are long-lived plasma cells located?
They reside in the bone marrow where they receive survival signals from stromal cells
what is the function of long-lived plasma cells?
They are a source of long-lasting high-affinity class-switch antibody
what are plasma cells?
Antibody factories
where do memory B cells come from?
they arise from the germinal centre reaction
what are the features of memory B cells?
they have inherited the genetic changes from the germinal centre reaction
- express high-affinity antibody
- have undergone antibody class switching
They express higher levels of MHC II and co-stimulatory molecules than naive B cells
where are memory B cells found?
They populate the spleen and lymph nodes and circulate through the blood
how do memory B cells express antibody?
Express surface Ig but do not secrete antobody
- Quickly generate antibody producing plasma cells when they re-encounter antigen
what do most vaccines rely on?
B cell memory
what are memory T cells?
long-libed cells that survive after the contraction of the effector phase
what is needed for survival of memory T cells?
IL-7 and IL-15
- memory T cells also need to contact self-peptide:self MHC complexes to continue to proliferate (does not need to be specfic antigen)
what are the features of memory T cells?
-Higher precursor frequency
- Different activation requirements and cell surface proteins from naive and effector cells
- Memory T cells divide more frequently than naive T cells
- Memory pool size is dictated by a balance between cell proliferation and cell death
what do memory T cells need to be effective?
- know where to go
- Be able to get there quickly or already be there
- Have good fighter equipment
what are the differences between memory T cells and effector T cells?
- They proliferate more than naive T cells and to a lower level of antigen dose
- Require less co-stimulation for activation than naive cells
- Produce cytokine faster and retain their polarised phenotype
- May be strategically positioned in the tissue where the pathogen is likely to be encountered
what are the features of central memory?
-Express lymph-node homing molecules
- Slower than effector memory cells to produce cytkine
what are the features of effector memory?
-lack lymph-node homing molecule expression
- rapidly produce cytokine upon antigenic stimulation
what are lymph noe homing molecules and where are they expressed?
Lymph node homing molecules CCR7 and CD62L are co-expressed on a subset of CD4 and CD8 memory T cells in human peripheral blood
what are Tcm and Tem cell subsets?
Tcm is CCR7+ (not very good at making cytokine)
Tem is CCR7-
what is the difference between Tcm and Tem cell subsets?
Tem persist in tissue and are functionally superior to Tcm
- discovery that after viral or bacterial infection memory CD8 T cells moved to non-lymphoid tissues and remained as long-lived memory cells. These cells were more lytic than memory CD8 T cells from the spleen
what are the features of tissue resident memory?
-Lack lymph-node homing molecule expression, express the integrin CD103 and CD69. Do not recirculate in the blood.
- Rapidly produce cytokine upon antigenic stimulation
how where Trm T cells discovered?
Discovery that after infection memory CD8+ T cells can remain in tissues after infection has cleared without recirculating in the blood
where do you not find resident memory T cells?
in the blood
what is the linear model of memory T cell development?
Memory cells develop directly from differentiated effector cells
what is the evidence that supports the linear model of memory T cell development?
Adoptive transfer studies show adoptively transferred effect CD4 and CD8 T cells develop into memory populations that retain similar functional polarisation to the effect cells
what is the progressive model of memory T cell development?
The degree of activation dictates the fate of a cell
what evidence supports the progressive model of memory T cell development?
transcriptional profile analysis of naive, memory, and effector CD8 T cells generated after vaccination, suggest cumulative antigen stimulation drives naive T cells to differentiate into memory T cells, then into terminally differentiated effector T cells
what is the divergent model of memory T cell development?
T cells are destined to an effector or memory lineage due to asymmetric cell division
what supports the divergent model of memory T cell development?
clustering of receptors and molecules at the immunological synapse causes uneven distribution of cell contents in daughter cells
what is innate immune ‘memory’?
Epigenetic changes in monocytes result in a long-lasting enhanced protection against infection
what is the evidence for innate immune ‘memory’?
many vaccines have effects that extend beyond the targeted disease
