Acquired Immunity

Question 1

What is hapten?

Answer 1

a small molecule that is unable to elicit an immune response on its own due to small size

Question 2

What is a carrier?

Answer 2

a larger molecule (protein) that is coupled to hapten to render the hapten+carrier complex immunogenic

Question 3

What is an epitope?

Answer 3

“antigenic determinant” part of antigen that binds lymphocyte antigen receptors, can be multiple on a single antigen

Question 4

What is the central theme of the acquired immune system?

Answer 4

lymphocytes express receptors with one unique specificity to bind specific antigens

Question 5

What is the carrier effect? what do B & T cells bind?

Answer 5

since haptens are too small to induce an immune response, carriers bind to hapten -> B cells recognize hapten & T cells recognize carrier

Question 6

What is linked recognition?

Answer 6

in the carrier effect, T & B cells recognize same antigen, but different epitopes

Question 7

What are autologous antigens?

Answer 7

self-antigens, only immunogenic when autoimmune disease is present

Question 8

What are syngeneic antigens?

Answer 8

from genetically identical individuals, no immune response if transferred to twin

Question 9

What are allogeneic antigens?

Answer 9

from genetically unrelated individuals from same species, immune response occurs

Question 10

What are xenogeneic antigens?

Answer 10

from different species, immune response occurs

Question 11

What factors influence immunogenicity?

Answer 11

large size, complex, moderate dose, subcutaneous>intraperitoneal>intravenous> intragastric, particulate form, w/ adjuvant, greatly differ from self

Question 12

What type of antigen response and what line of defense is acquired immunity?

Answer 12

antigen-specific immune response, second line of defense

Question 13

What stimulates defense mechanisms of acquired immunity?

Answer 13

antigen exposure

Question 14

How fast is acquired immunity response?

Answer 14

delayed onset, days or weeks

Question 15

What duration does acquired immunity provide?

Answer 15

long-term, with enhanced subsequent response

Question 16

What are the two types of immunity that make up acquired immunity? their process? type of targeted pathogen?

Answer 16

humoral: B cells -> plasma cells -> secrete antibodies *important for extracellular pathogens
Cell-mediated: cytotoxic T cells kill infected cells, helper T celsl regulate humoral *important for intracellular pathogens

Question 17

What are naive cells?

Answer 17

lymphocytes that encounter an antigen for the first time

Question 18

What are the phases of acquired immune responses?

Answer 18

antigen recognition -> lymphocyte activation -> cell proliferation -> differentiation into effector cells -> kill infection -> die by apoptosis or live as memory cells

Question 19

How many different antigens can each antigen receptor bind?

Answer 19

one, this is specificity

Question 20

Where does the antigen receptor bind epitope?

Answer 20

variable region

Question 21

What are antigen receptors expressed by B cells called?

Answer 21

antibody, surface immunoglobulin (secreted later), B cell receptor

Question 22

What are antigen receptors expressed by T cells called?

Answer 22

T cell receptor, NOT secreted

Question 23

What types of antigens to B and T cells recognize?

Answer 23

B: bind antigens alone, single specificity, intact antigens
T: bind peptides AND MHC, dual specificity, fragments

Question 24

How are B and T cells activated?

Answer 24

B: associates with Ig-alpha & Ig-Beta (NOT antibody molecules)
T: associates with CD3 complex (4 different proteins)

Question 25

Where do the primary and secondary signals (costimulatory) come from?

Answer 25

primary: antigen receptor complex
secondary (required for naive lymphocytes):
-B: CD40 by T cell
-T: CD28 by dendritic cell

Question 26

What is anergy?

Answer 26

for naive cells, if signal 2 is missing the cell is driven into unresponsive state, helps prevent autoimmune disease

Question 27

What characteristics make acquired immune responses so effective?

Answer 27

specificity, diversity, regulation (antigen eliminated, short effector cell life, regulatory T cells), distinguishing (self vs non-self), memory, clonal selection

Question 28

What is clonal selection theory?

Answer 28

specific lymphocytes made before exposure to non-self antigens, have unique specificity, result of random process, selective activation by antigen, single cell produces many clones with same specificity

Question 29

What is deletion?

Answer 29

lymphocytes express receptor for self antigen -> if immature a negative signal is sent -> the autoreactive cell is killed *helps prevent autoimmune diseases