33: Immunological Memory

Why is immunological memory helpful

Helps fight subsequent exposure

Which components of the immune system have memory

Adaptive immune system (B and T cells)

Which Ab is predominant in primary infections and exposure

IgM

Which Ab is predominant in subsequent infections and exposures

IgG

Which Ab is predominant in the mucosa

IgA

Which Ab is predominant in parasite infections

IgE

Where do B cells live

Secondary lymphoid organs, bone, mucosa

Where do T cells live

Secondary lymphoid organs and peripheral tissues

Purpose of effector T cells

Does the work during the beginning of the immune response

Terminal differentiation of a B cell that produces Abs

Plasma cells

Terminal differentiation of a B cell that circulates

B memory cell

Theories for what turns a B cell into a memory vs plasma cell

• T cell instruction

• Quirk of replication

• T cell and BCR stim

Three fates of the B cell

• Stays in lymphoid organs to replicate

• Memory cell

• Plasma cell

Features of a memory B cell

• BCR

• MHC

• Circulates

• Proliferates

• Can still do affinity maturation and class switching

Features of a plasma cell

• No BCRS

• Low MHC

• Stuck in bone marrow

• No proliferation

• No Ab modification

Difference between Ag targeting in a primary response vs a secondary/memory response

Secondary response is usually more specific to the pathogen

Are there more B cells recruited in a primary response or a memory response

Primary

Are there more Abs in a primary response or a memory response

Memory response

Types of T cells

• Naive T cells

• Central memory T cells

• Effector memory T cells

• Effector T cells

Largest population of T cells in a primary response

Effector T cells

When are memory T cells produced

At the end of an infection

Why are T cells harder to study than B cells

B cells secrete specific antibodies. T cells secrete a bunch of things that are secreted by other types of cells

How to measure T cells

They have to be stained and put through a flow cytometer to eval receptor expression

What do T cell markers inform

• Migration

• Localization

• Differentiation

• Activation and function

Categories of immune cell location

Central or peripheral

What controls immune cell migration

Chemokines interacting with receptors

T cell marker that keeps T cells in central tissues (Gatekeepers to the LNs)

CCR7 and CD62L

Do naive T cells express CCR7 and CD62L

Yes

Do T central memory cells express CCR7 and CD62L

Yes

Do T effector memory cells express CCR7 and CD62L

No

Do T effector cells express CCR7 and CD62L

No

T cell marker key for activation

CD45

Forms of CD45

• CD45R_A: longer splice, more interaction specific

• CD45R_O: shorter splice

What form of the CD45 receptor do naive T cells express

CD45R_A

What form of CD45 do T central memory cells express

CD45R_O

What form of CD45 do T effector memory cells express

CD45R_O

What form of CD45 do T effector cells express

Either

Which T cells are best at differentiation

Naive T cells

Which T cells are best at killing

T effector cells

Relationship of LN homing and effector function

They are opposite qualities: if a T cell is an effector, it cannot be confined to lymphoid organs

Exception: type of effector T cell that is allowed in the LN

T_FH cells (helps B cells)

Type of memory T cell that lives in peripheral tissues (not circulating)

Resident memory CD8 cells

Characteristics of resident memory CD8 cells

• No differentiation or proliferation

• Long lived

• Stays in the tissues

Purpose of all this organization with receptors

To divide labor and produce an effective memory response later