Lecture 33 Flashcards
What type of antibody-producing cells dominate the primary B cell response?
Most IgM-producing cells (some IgD) come from the primary focus.
Where do some B cells go during the primary response to improve their antibody characteristics?
To the germinal center, where they undergo somatic hypermutation and class switching late in the response.
Do memory B cells produce IgM in the secondary response?
Yes, some memory B cells still make IgM.
What is the most common antibody isotype produced by memory B cells during the secondary response?
IgG (some also produce IgA and IgE).
What process allows antibodies to increase in affinity during repeated immunization?
Somatic hypermutation and affinity maturation.
Can memory B cells re-enter the germinal center?
Yes, they can re-enter to undergo further affinity maturation.
What type of surface immunoglobulin isotype do memory B cells express?
Class-switched isotypes, such as IgG.
What molecules are expressed at higher levels on memory B cells compared to naïve B cells?
MHC class II, CD40, and receptors for survival and proliferation.
Why do memory B cells present antigen more efficiently than naïve B cells?
Because they express higher levels of MHC II and CD40, helping them interact more effectively with TFH cells.
Where do memory B cells circulate and reside after activation?
They circulate through the blood and reside in the spleen and lymph nodes.
What happens to most effector T cells after a pathogen is cleared?
At least 90% die by apoptosis, leaving behind antigen-specific memory T cells.
How are naïve, effector, and memory T cell subsets distinguished in mice?
By their surface markers.
Are memory T cells phenotypically closer to naïve or effector T cells?
Effector T cells.
What makes memory T cells easier to activate than naïve T cells?
They require less co-stimulation and express unique receptors (e.g., high levels of CD28).
Do memory T cells still need contact with p:MHC for activation?
Yes, but they are more sensitive and respond faster than naïve T cells.
What happens to memory T cells upon reactivation?
They become effector T cells.
Where are central memory T cells (TCM) found and what do they do?
They reside in/travel between secondary lymphoid tissues and are rapidly reactivated upon antigen exposure.
What is the differentiation potential of TCM cells?
They can differentiate into various subsets depending on the cytokine environment.
Where do effector memory T cells (TEM) travel and function?
They move to and between tertiary tissues, contributing to first-line defense and quickly regaining effector function.
What distinguishes tissue-resident memory T cells (TRM)?
They are permanent residents in previously infected tissues and respond quickly upon reinfection.
Where are CD8+ TRM cells commonly found?
In multiple tissues.
What factors influence whether a T cell becomes a memory T cell?
Cytokines (IL-7, IL-15), Notch1, and the strength of antigen interaction.
What is the role of IL-7 in memory T cell development?
It promotes survival by increasing expression of Bcl-2, an anti-apoptotic factor.
What happens to IL-7 receptor alpha (IL-7Rα) during effector T cell differentiation?
It is downregulated but retained or reacquired by cells fated to become memory T cells.
