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
