Lecture 13 - Immunological memory Flashcards
Primary vs secondary vs tertiary responses to infections: time taken roughly
~7-10 days
~3 days
~? very short
Memory cells: what causes their formation, where are they generated, where are they typically found, do they have any specific cell surface markers, what antibodies do they most frequently express, how long do they live, and how are their numbers maintained?
Mechanism not fully understood, activation of B cells causes differentiation into memory cells as well as proliferation
Generated in germinal centres
Secondary lymphoid organs and circulation
CD27
High affinity class switching Abs (IgA, IgE, IgG(?))
Very long
Potentially proliferation may be due to cytokines made by memory cells or other immune cells
CD27: what is it, where is it found, and what medical potential is there for it?
Found in memory cells
Cancer immunotherapy - checkpoint inhibitor
Memory response vs initial response: frequency of antigen-specific B cells, isotype of antibody produced, and
1:10⁴-1:10⁵ vs 1:10²-1:10³
IgM>IgG vs IgA, IgG
Memory cells: why do they trigger quicker responses than normal B cells?
High surface immunoglobulin (BCR) expression
High affinity surface BCR
High MHC II expression
High co-stimulatory molecule expression
These mean they have an increased ability to interact with Th cells and so can respond at lower antigen doses and also have already undergone class switching and affinity maturation
Bone marrow slide
Memory cell differentiation: transcription factors involved
B -cell - BLIMP-1
Memory cell - BCL-6
Long-lived plasma cells
BLIMP-1
BCL-6
Memory t-cells
~100-1000x levels of initial naive T-cells
IL-7 and IL-15 for survival as well as self-MHC antigen to continue proliferation
Central memory t-cells - CCR7
Effector memory t-cells - CCR3/5
Tissue-resident memory t-cells
Blurred lines between central and effector t-cells
B and T cell differences: class switching, affinity maturation, and identification
No class switch in t-cells
No affinity maturation in t-cells
T-cells harder to identify due to lacking the prior two features
Memory T-cell formation
- Long-lived memory cell differentiation
- IL-7 and
- Interactions with self antigen to maintain proliferation
IL-7
IL7-α
IL-7 receptor α
Expressed by memory T-cells
Central memory t-cells:
CCR7
Peripheral lymphoid organs
- Quick Increase in CD40
- Quickly relocate
Take longer to generate but last longer
