Immunological Memory Flashcards
Which immune molecules remain in the body following infection?
Antibodies
What kind of response is triggered in secondary infections?
A faster and stronger secondary immune response.
Specific high affinity antibodies are produced
Where do long lived memory T and B cells originate?
In the secondary lymphoid tissues
Why do memory cells respond more robustly?
Pathogen specific memory cells outnumber naive specific counterparts.
Memory cells are activated more rapidly
Memory B cells have already undergone isotype switching, somatic hypermutation, and affinity maturation.
What happens to normal lymphocytes after exposure to an antigen?
They die by apoptosis
What happens to memory cells over a long period of time of not encountering the antigen?
Individual memory cells die but they continue dividing and replenishing in response to signals from IL-7 and IL-15
What cytokines promote survival of memory T cells?
IL-7 and IL-15
Where does memory B and T cell renewal take place?
In bone marrow and is driven by interactions with stromal cells and cytokines
What are the defining features of memory B cells?
Memory B cells have surface Ig and do not secrete antibodies.
Memory B cells are not long like effector B cells.
Memory B cells express CD27.
What is the difference between antibody responses produced in primary response and secondary response?
Primary response is characterized by production of IgM, IgG, IgA, and IgE. Antibodies have lower affinity (low somatic hypermutation).
Secondary response does not produce much IgM. Antibodies have higher affinity (high somatic hypermutation).
What is used to distinguish memory T cells from naive and effector T cells?
Combination of CD45RO, CD45RA, CD62L, and CCR7.
What must happen prior to secondary response taking place?
The pathogen must bypass innate defenses.
How do memory T cells differ from naive T cells?
Memory T cells can be activated directly at sites of infection (rather than through secondary lymphoid organs) by DCs and macrophages that present re-infecting antigen.
Activation requiredments for memory T cells are less demanding than naive T cells as they do not need co-stimulation via CD28/B7
What other memory T cells can be activated in secondary lymphoid tissue?
Tfh cells
What is the difference between central and peripheral memory T cells?
Peripheral T cells act directly in the tissues. These tissues do not have L-selectin and CCR7 which is important for cells localized to lymphoid tissue. Before activation have limited effector functions.
Central T cells wait in the bone marrow to be triggered and then act all over. They have L-selectin and are CCR7 positive. By patrolling they can respond immediately to re-infection.
