Acquired Immunity Flashcards
What is hapten?
a small molecule that is unable to elicit an immune response on its own due to small size
What is a carrier?
a larger molecule (protein) that is coupled to hapten to render the hapten+carrier complex immunogenic
What is an epitope?
“antigenic determinant” part of antigen that binds lymphocyte antigen receptors, can be multiple on a single antigen
What is the central theme of the acquired immune system?
lymphocytes express receptors with one unique specificity to bind specific antigens
What is the carrier effect? what do B & T cells bind?
since haptens are too small to induce an immune response, carriers bind to hapten -> B cells recognize hapten & T cells recognize carrier
What is linked recognition?
in the carrier effect, T & B cells recognize same antigen, but different epitopes
What are autologous antigens?
self-antigens, only immunogenic when autoimmune disease is present
What are syngeneic antigens?
from genetically identical individuals, no immune response if transferred to twin
What are allogeneic antigens?
from genetically unrelated individuals from same species, immune response occurs
What are xenogeneic antigens?
from different species, immune response occurs
What factors influence immunogenicity?
large size, complex, moderate dose, subcutaneous>intraperitoneal>intravenous> intragastric, particulate form, w/ adjuvant, greatly differ from self
What type of antigen response and what line of defense is acquired immunity?
antigen-specific immune response, second line of defense
What stimulates defense mechanisms of acquired immunity?
antigen exposure
How fast is acquired immunity response?
delayed onset, days or weeks
What duration does acquired immunity provide?
long-term, with enhanced subsequent response
What are the two types of immunity that make up acquired immunity? their process? type of targeted pathogen?
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
What are naive cells?
lymphocytes that encounter an antigen for the first time
What are the phases of acquired immune responses?
antigen recognition -> lymphocyte activation -> cell proliferation -> differentiation into effector cells -> kill infection -> die by apoptosis or live as memory cells
How many different antigens can each antigen receptor bind?
one, this is specificity
Where does the antigen receptor bind epitope?
variable region
What are antigen receptors expressed by B cells called?
antibody, surface immunoglobulin (secreted later), B cell receptor
What are antigen receptors expressed by T cells called?
T cell receptor, NOT secreted
What types of antigens to B and T cells recognize?
B: bind antigens alone, single specificity, intact antigens
T: bind peptides AND MHC, dual specificity, fragments
How are B and T cells activated?
B: associates with Ig-alpha & Ig-Beta (NOT antibody molecules)
T: associates with CD3 complex (4 different proteins)
Where do the primary and secondary signals (costimulatory) come from?
primary: antigen receptor complex
secondary (required for naive lymphocytes):
-B: CD40 by T cell
-T: CD28 by dendritic cell
What is anergy?
for naive cells, if signal 2 is missing the cell is driven into unresponsive state, helps prevent autoimmune disease
What characteristics make acquired immune responses so effective?
specificity, diversity, regulation (antigen eliminated, short effector cell life, regulatory T cells), distinguishing (self vs non-self), memory, clonal selection
What is clonal selection theory?
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
What is deletion?
lymphocytes express receptor for self antigen -> if immature a negative signal is sent -> the autoreactive cell is killed *helps prevent autoimmune diseases
