Immunological memory and the secondary immune response

Question 1

Deficiencies in innate mechanisms are _____

Answer 1

Rare

Question 2

Adaptive

Answer 2

• specificity
• memory
• affinity maturation (B cells)
• make possible vaccination

Question 3

Acute infection

Answer 3

Establishment of infection –> induction of adaptive response –> adaptive immune response –> immunological memory

Question 4

Extracellular

Answer 4

• interstitial spaces, blood, lymph = antibodies, complement, phagocytosis, neutralization
• epithelial surfaces = antibodies (IgA), antimicrobial peptides

Question 5

Intracellular

Answer 5

• cytoplasmic = cytotoxic T cells, NK cells, helper T cells

- vesicular = T cell and NK cell dependent macrophage activation

Question 6

Different types of immune effector mechanisms are effective against various pathogens

Answer 6

• viruses: humoral immunity (Ig) and cell-mediated immunity (CD4, CD8
• bacteria: humoral immunity (some cell-mediated)
• fungi: humoral and CD4
• protozoa: humoral and CD4
• worms: CD4

Question 7

Successful primary immune response

Answer 7

• clears the infection
• temporarily strengthens defenses to prevent re-infection
• establishes a long term immunological memory to ensure that subsequent infections with the same pathogen will provoke a faster, stronger, secondary immune response (memory)

Question 8

After successful termination of infection by the primary response, elevated levels of _____ will be present in blood/lymph , or at mucosal surfaces

Answer 8

High-affinity pathogen-specific antibody

Question 9

______ produced during a primary immune response

Answer 9

Effector and memory B and T cells

• most activated T cells become effector cells
• some activated and/or effector cells become long-lived memory cells

Question 10

Cell-cell interactions in a secondary immune response

Answer 10

• effector memory T cells can be activated directly at the site of infection by DC and macrophages
• activation requirements are less demanding since they do not require co-stimulation

Question 11

Unimmunized donor primary response

Answer 11

• frequency of specific B cells: 1:10^4-1:10^5
• isotype of antibody produced: IgM>IgG
• affinity of antibody: low
• somatic hypermutation: low

Question 12

Immunized donor secondary response

Answer 12

• frequency of specific B cells: 1:10^3
• isotype of antibody produced: IgG, IgA
• affinity of antibody: high
• somatic hypermutation: high

Question 13

The _____ and ____ of antibody increases after successive immunizations with the same antigen

Answer 13

Amount; affinity

Question 14

Smallpox vaccine

Answer 14

Persistance of immunological memory in the absence of antigen

Question 15

How does IgG antibody suppress the activation of naive B cells?

Answer 15

Cross-linking BCR and FcgR on B cells

Question 16

Primary response

Answer 16

Naive B cell binds pathogen –> naive B cell is activated and becomes antibody producing plasma cell –> production of low-affinity IgM antibodies

Question 17

Secondary response with naive B cell

Answer 17

Bind pathogen coated with specific antibody –> negative signal is given to naive B cell to prevent activation –> no production of low affinity IgM antibodies

Question 18

Secondary response with memory B cell

Answer 18

Binds pathogen coated with antibody –> memory B cell is activated and becomes an antibody producing plasma cell –> production of high affinity IgG, IgA, and IgE antibodies

Question 19

How does influenza escape from immunological memory?

Answer 19

Highly mutable, undergoes original antigenic sin

Question 20

Original antigenic sin

Answer 20

The first influenza strain to infect an animal constrains the immune response to other strains
- virus will drop old epitopes and add new ones, which induces a new primary response

Question 21

How does influenza enter the cell?

Answer 21

Uses hemagglutinin protein to bind to sialic acid attached to human cell-surface proteins
- vaccines prevent this by presence of neutralizing antibodies against viral hemagglutinin

Question 22

Cytomegalovirus infection

Answer 22

Latent virus, goes thru periods of activation that are quelled by immune responses

• increase in viral load triggers rapid increase in numbers of virus specific effector T cells
• numbers fall back once virus is under control, leaving a sustained lower-level of long-lived, virus specific memory T cells

Question 23

Why is it difficult to detect T cell receptors?

Answer 23

They are membrane bound and never secreted

Question 24

T cell differentiation

Answer 24

Naive T cell sees antigen

• memory cells may derive directly from activated naive T cells –> central memory cells express CCR7 and remain in lymphoid tissue –> effector memory cells lack CCR7 and migrate to tissues
• effector T cells differentiate, secrete cytokines, and express receptors –> some effector cells may become quiescent memory cells –> most effector cells die

Question 25

Ubiquitous responses of innate immunity (0-4 hrs)

Answer 25

Infection –> recognition by preformed, nonspecific effectors –> removal of infectious agent (no clinical signs)

Question 26

Induced responses of innate immunity (4-96 hrs)

Answer 26

Infection –> recruitment of effector cells –> recognition, activation of effector cells –> removal of infectious agent

Question 27

Adaptive response (>96 hrs)

Answer 27

Infection –> transport of antigen to lymphoid organs –> recognition by naive B and T cells –> clonal expansion and differentiation to effector cells –> removal of infectious agent

Question 28

Protective immunity

Answer 28

Re-infection –> recognition by preformed antibody and effector T cells –> removal of infectious agent

Question 29

Immunological memory

Answer 29

Re-infection –> recognition by memory B cells and T cells –> rapid expansion and differentiation to effector cells –> removal of infectious agent

Question 30

____ and ___ accumulate in the course of the primary immune response

Answer 30

Effector T cells and antibodies

Question 31

Antibodies in the secondary immune response

Answer 31

Are of higher affinity than in the primary immune response and are of isotypes other than IgM

Question 32

Only ____ are activated

Answer 32

Memory lymphocytes

- activation of naive cells is suppressed

Question 33

Secondary immune response, immune system devotes resources to producing _____

Answer 33

High affinity antibodies and antigen-specific T cells that rapidly clear the invading pathogen before

Question 34

Maintenance of memory cells

Answer 34

Does not require persistance of the original antigen

- survival signals are provided by cytokines IL-7 and IL-15