Chapter 11

What is the purpose of immunological memory?

To produce a faster, stronger adaptive response upon reexposure to the same pathogen.

clonial selection

allow concentration of effector mechanisms to effeciently target and clear an infection

• basically to recoginze and selecting correct lymphocyte

How long can a primary adaptive immune response take?

Up to 14 days.

• needs interaction with dendritic cells and engagement of T cell to stimulate B cell activation

How quickly can a secondary immune response clear infection?

About 3–4 days.

Why is the secondary immune response faster?

Memory B and T cells formed during the primary response activate rapidly.

What processes improve memory B-cell antibodies?

Somatic hypermutation and isotype switching.

somatic hypermutation

create changes in antibody variable region

isotype switching

changes antibody classes

Why is naïve B-cell activation limited during secondary responses?

To favor rapid production of high-affinity antibodies by memory B cells.

What is the role of long-lived memory lymphocytes?

To respond rapidly when the same pathogen is encountered again.

clonal expansion

• Selected cell proliferates and differentiates.

• Produces daughter/effector cells that recognize the same antigen.

What are the four memory T-cell subpopulations?

TSCM, TCM, TEM, and TRM.

What is special about T memory stem cells (TSCM)?

They self-renew and can differentiate into other memory T-cell types.

• long termed

Where are TSCM cells found?

Circulatory and peripheral tissues.

Which memory T cells circulate through secondary lymphoid tissues (like lymphy nodes)?

Central memory T cells (TCM).

Central memory T cells (TCM) mode of activation simliar to

naive T cell

What does increased IL-2 expression allow TCM cells to do?

Activate and differentiate into effector cells after antigen exposure.

What is the main function of effector memory T cells (TEM)?

Rapidly become effector cells in peripheral tissues without lymphoid migration.

Which cytokines are associated with TEM cells?

IFN-γ and TNF-α.

What makes resident memory T cells (TRM) unique?

They remain in peripheral tissues and do not reenter circulation.

• DOES NOT MOVE

How do TRM cells protect against reinfection?

Rapid activation and effector function at potential infection sites.

Which CD45 isoform is expressed by naïve T cells?

CD45RA.

• RA = naive

Which CD45 isoform is expressed by memory T cells?

CD45RO, which supports more efficient activation signaling.

• RO is memory

CCR7

help lympocytes migrate into lymphoid tissue

Which memory T cells express CCR7 and L-selectin?

Central memory T cells (TCM).

CD103

tissue retention/ residency

Which marker is characteristic of resident memory T cells?

CD103, which binds epithelial cells.

Which cells activate naïve B cells in secondary lymphoid tissues?

CD4 helper T cells.

where does the activation for naïve B cells in secondary lymphoid tissues hapen?

• t cell zone

what does activated B cell produce

IgM

What happens to B cells in germinal centers?

They undergo somatic hypermutation and isotype switching.

What do activated memory B cells produce?

High-affinity, isotype-switched antibodies.

• for secondary immune response

How does IgG suppress naïve B cells during secondary responses?

Antigen-bound IgG engages inhibitory FcγRIIB1 on naïve B cells.

memory B cells are localized in

spleen and migrate to other secondary lymphoid tissue through circulatory and lymphatic system

How does IgG suppress naïve B cells during secondary responses?

Antigen-bound IgG engages inhibitory FcγRIIB1 on naïve B cells.

Which Fc receptor inhibits naïve B-cell activation?

FcγRIIB1.

memory B cell devolpment pathway

naive b cell recoginzes antigen → cd4 helper t cell activation signal → geminal center → somatic + isotype → plasma cell (antibodies) and memory B cell (re exposurer)

how does naive lymphocytes obtain surival signals

through T cell receptor or immunoglobins

What is herd immunity?

Indirect protection when widespread immunity reduces pathogen transmission.

Variolation

inoculating an individual with smallpox material such as pustule fluid.

Vaccination

inoculating an individual with cowpox material

• considered safer

What is the primary goal of vaccination?

Generate protective memory T and B cells.

Vaccination

• induce a primary immune response

• promotes activation of the exact lymphocytes needed to combat the actual pathogen

inactivated vaccine

A vaccine containing pathogens killed or inactivated by heat, irradiation, or chemicals.

• CANT REPLICATE

Why do inactivated vaccines often require boosters?

The initial dose may not provide a sufficiently protective immune response.

What is a live attenuated vaccine?

A weakened living pathogen that survives in the host without causing disease.

• Can replicate but not as much

Why can live attenuated vaccines produce strong immunity?

They closely mimic natural infection.

What is the purpose of a toxoid vaccine?

Induce neutralizing antibodies against inactivated bacterial toxins.

• target toxin

how are toxiod vaccine inactivated

formalin or heat treatement aka toxoids

How do subunit vaccines prevent pathogen entry?

They induce antibodies against pathogen adhesion molecules.

• selected parts of the antigen

what are subunit vaccines used for

• primary immune response

• protects aganist pathogen adhesion

• prevent entry into target cells

What is the principle behind conjugate vaccines?

Link a weak polysaccharide antigen to a strong protein antigen such as a toxoid.

How do conjugate vaccines improve polysaccharide immunity?

They recruit T-cell help so B cells produce opsonizing antibodies.

How do recombinant vector vaccines work?

Harmless bacteria or attenuated viruses deliver genes encoding pathogen antigens.

How are DNA vaccines different from recombinant vector vaccines?

They deliver antigen-encoding DNA directly instead of using a microbial vector.

• DNA goes straight in

How do mRNA vaccines work?

Host cells translate delivered mRNA into antigen, triggering adaptive immunity.

Why are vaccine mRNA nucleotides modified?

To reduce recognition as PAMPs and limit unwanted innate immune activation.

What is the role of an adjuvant in vaccination?

Induce inflammation that strengthens immune activation and costimulation.

Why do naïve T and B cells require costimulation?

For proper activation and to prevent anergy.

What are the two requirements of an effective vaccine?

• Promote clonal selection of protective lymphocytes

• ensure proper costimulation.

How does inflammation promote naïve T-cell activation?

It increases B7 expression on dendritic cells, allowing costimulation of naïve T cells.

What must successful vaccination promote?

Clonal selection and expansion of protective lymphocytes along with an inflammatory response.

What is the role of adjuvants in vaccines?

To induce inflammation and strengthen the immune response.

how are most vaccine given

injected intramuscularly

how is live attenuated vaccine given

orally

Live attenuated rotavirus vaccine is given orally

• activates an adaptive immune response within mucosa-associated lymphoid tissue.

• promotes the activation of lymphocytes in locations where the pathogen is most likely to infect