Immunology - Antigen Recognition in the Adaptive System II

01/23/2025

Surface lymphocytes identify lymphocytes as ______

B/T lymphocytes

What does it mean to be clonally distributed?

Specific for each antigen

Antigen receptors (AgR) are assembled during _____

Lymphocyte development

What is the purpose of having multiple checkpoints?

To test developing cells

What is the first checkpoint?

Production of 1 AgR chain

What is the second checkpoint?

Assembly of complete AgR

What are the signals from Pre-AgR and AgR required for?

Survival, proliferation, maturation

What is positive selection?

Facilitates survival of potentially useful lymphocytes

What is negative selection?

Eliminates/changes cells with AgR that bind self too much

What is clonal deletion?

Lymphocytes die by apoptosis

What is receptor editing?

Replacement of heavy/light chain on auto reactive B cells with new rearrangment

What is a Pre-BCR?

Surrogate light chains and u heavy chains

What does the allelic exclusion do?

Shuts off recombination on other chromosome, express heavy chain from 1 inherited parental allele, activates light chain recombination

What gets rearranged first, heavy or light chains?

Heavy

What is BCR (IgM)?

u heavy chain and k light chain

Where does final maturation of B cells happen?

Spleen

A mature B cell consists of the co-expression of _____

IgM and IgD

Where do B cells mature into pre-B and immature B cells?

Bone marrow

Future T cells leave bone marrow and enter the thymus as _____

Double negative cells

Some future T cells may undergo _____

V(D)J recombination

What does a twice unsuccessful B chain result in?

Cell death

What does a successful B chain and pre-Ta result in?

Pre-TCR or Pre-T cells

What does a successful arrangement of the alpha chain result in?

alpha + beta (aB TCR)

What does selection depend on?

Ag recognition, keep useful cells, affinity for self

What does strong binding of self proteins via MHC result in?

Death, negative selection

What results when AgR doesn’t bind/signal?

Death by neglect

What results when there is weak binding through AgR?

Survival, positive selection

If MHC I present antigen, what gets lost?

CD4

If MHC II present antigen, what gets lost?

CD8

What does it mean to be immunocompetent?

Mature lymphocyte capable of recognizing specific antigen and mediating response

What is a naive cell?

Never encountered AgR specific antigen

Which lymphoid tissues do naive lymphocytes circulate between?

2 - spleen and lymph nodes

3 - previously infected tissues

Lymphocytes* migrate across ____ in lymph nodes into paracortex

High endothelial venules

What is the first step of surveillance?

Extravasation/entrance

What drives extravasation?

Sequential activation of surface molecules

What is the second step of surveillance?

Movement

What is the third step of surveillance?

Exit

During step 2 of surveillance, where do dendritic cells go?

Everywhere

During step 2 of surveillance, where do T cells go?

FRC network

During step 2 of surveillance, where do B cells go?

FDC

What is S1P responsible for?

Controlling retention and release of the lymphocytes through lymph nodes

What results in the increase of S1PR1?

No antigen presence

What do lymphocytes use to move through lymph nodes to find antigen?

FDC, FRC, chemokine

CD4+ cells differentiate into ______

Th subsets

Which cell migrates to follicles and helps activate B cells?

Follicular helper T cells

What activates CD8+ cells?

Multicellular interaction

What “licenses” a CD8+ cell?

Activated Th cell

Fully activated CD8+ cells proliferate and differentiate into _____

Effector CTLs and memory cells

B cells detect antigens in ____

Follicle

B cells get help from _____

Ag-specific T cells

Memory B cells differentiate into ______ and produce ______

Plasma cells; IgM

Memory cells can form ____

Germinal center

What is the purpose of germinal center?

Makes better antibodies, binds antigen, improve biological function

To initiate a response, what gets unregulated and what gets downregulated?

S1PR1; L-selectin

Where do early IgM producers go to?

Lymph node medulla

Where do IgG go to?

Bone marrow

Where do IgA go to?

Mucosal immune tissues

Effector and memory T cells follow _____

Chemokine cues

How long does it take for contraction/resolution to happen?

10-14 days

What are the 2 mechanics within contraction/resolution?

Fas-FAsL and regulatory T cells