Ch 13: Adaptive Immunity Flashcards
(51 cards)
What is adaptive immunity?
specific response that is acquired after exposure to antigens
antigen receptors on lymphocytes are involved in recognition of self vs. nonself
specificity of response is stored in immunologic memory and can be used to fight subsequent infections
What is the general overview of what happens during infection and how the adaptive immune system is activated?
microbe PAMPs bind to PRRs on innate cells, which then release proinflammatory cytokines (HARMFUL!)
dendritic cells process and present nonself antigens to T lymphocytes
Helper T cells are activated and use cytokines to activate other immune cells
B cells/plasma cells produce antibodies that recognize nonself antigens
What is antigen presentation?
MHC (major histocompatibility complex) class I & class II receptors present peptide antigens to T-cell receptor
What is MHC I?
expressed by all nucleated cells
antigen presentation to CD8/cytotoxic T cells
responses vs. intracellular pathogens, such as viruses
What is MHC II?
expressed by dendritic cells, macrophages & B cells
antigen presentation to CD4/helper T cells
responses vs. extracellular pathogens, such as bacteria
What is a TCR?
TCR is comprised of two chains (α/β)
- associated with CD3 complex for intracellular signaling
What kinds of antigens do TCRs recognize?
TCR only recognizes peptide antigens presented with MHC
- needs CD4 co-receptor to recognize MHC II
- needs CD8 co-receptor to recognize MHC I
What is a BCR?
BCR is comprised of four chains (2 heavy / 2 light)
- associated with Igα and Igβ for intracellular signaling
recognizes epitope of native antigen
T cells also help activate B cells
What is clonal diversity in lymphocytes?
each mature lymphocyte possesses a single antigen receptor specificity
- 500+ gene segments that undergo “shuffling” or gene rearrangement (1013 possible combinations)
How does self-tolerance develop?
Clonal Deletion creates self-tolerance
- clones with BCR or TCR that recognize self antigens undergo apoptosis
- clones of non-self BCR or TCR created
What occurs once non-self lymphocytes develop and the host is presented with a non-self antigen?
clonal selection
- single naïve clone is stimulated by foreign antigen recognition (receptor binding)
clonal expansion
- proliferation and differentiation of activated lymphocytes
Go over the development of B and T Cells
Immature B and T Cells develop in the Bone Marrow
B Cells mature in the bone marrow
T Cells mature in the thymus
Mature Naive B and T Cells then migrate to the Lymph Nodes to wait for exposure to pathogens
Which molecule is used to present antigens by a cell infected with a virus, which is an intracellular pathogen?
PRR BCR TCR MHC I MHC II
MHC I
Which process during lymphocyte development is critical for preventing autoimmune responses?
Clonal selection
Clonal deletion
Clonal diversity
Clonal expansion
Clonal deletion
What happens during activation of naïve CD4 T lymphocyte by professional antigen presenting cell (APC)?
APC = macrophage or dendritic cell
phagocytosis of bacteria, fungi, viruses (exogenous antigens)
process and present peptides with MHC II to naïve CD4 T cell
T cell differentiates into helper T cell (TH cell)
What are the types of T Helper Cells?
TH1 activate TC and NK cells (intracellular pathogens) and macrophages, B cells (intracellular and extracellular pathogens)
TH2 activate eosinophils, B cells (eukaryotic parasites)
TH17 recruit neutrophils (bacteria and fungi)
Treg inhibit immune responses (termination)
memory CD4 T cell saved for later
What happens during activation of naïve CD8 T lymphocyte by professional antigen presenting cell (APC)?
APC = macrophage or dendritic cell
infected by virus (endogenous antigens)
process and present peptides with MHC I to naïve CD8 T cell
CD4 TH cell helps with activation
T cell differentiates into cytotoxic T cell (TC cell)
What are cytotoxic T Cells?
TCR/CD8 recognizes antigen/MHC I on virus-infected cell
- TC secretes perforins & granzymes
- triggers apoptosis of target cell
What are superantigens?
bacterial proteins that bind non-specifically to TCR
- T cell activation 100x greater than with normal antigens
- large release of cytokines → inflammation
- toxic shock syndrome toxin (TSST)
MHC II presentation of antigen to CD4 T cells directly results in a _______ response.
Natural killer cell Helper T cell Cytotoxic T cell Mast cell Red blood cell
Helper T Cell
Which chemicals are used by a cytotoxic T lymphocyte to kill virus-infected cells?
Antibodies Interferons Complement proteins Perforin and granzymes Defensin and MACs
Perforin and Granzymes
What are T-dependent antigens?
proteins bind to BCR and are processed by B cell and presented with MHC II to TCR of helper T cell
- bacterial surface proteins or adhesins
- viral capsid or envelope proteins
- exotoxins
What are T-independent antigens?
polysaccharides can only bind to BCR in native form (not presented with MHC)
- bacterial capsules
Walk through T-dependent B Cell Activation.
native antigen binds to B-cell receptor on naïve B cell
- endocytosis of antigen and processing
B cell presents antigen to activated TH cell
- MHC II/antigen is recognized by TCR/CD4
- chemical mediators from TH (e.g. IL-2)
B cell activation
- clonal expansion and differentiation
