Adaptive Immunity Flashcards
Principle defense against extracellular microbes
Humoral Immunity
Promotes destruction of intracellular microbes
Cell Mediated immunity
IL-7
Principle cytokine that stimulates the proliferation of B and T cell progenitors
Clonal selection hypothesis
Antigen receptors are produced by random DNA recombination events that are not dependent on or influenced by the presence of antigens
Somatic recombination
- VDJ combination
- Process of DNA recombination by which the functional genes encoding the variable regions of antigen receptors are formed during lymphocyte development
- Occurs only in immature B and T cells
Allelic exclusion
- Protein product of one productively recombined antigen receptor locus on one chromosome blocks rearrangement of the corresponding locus on the other chromosome
- Ensures that each lymphocyte will express a single antigen receptor and that all antigen receptors expressed by one clone of lymphs will have identical specificity
Which lymphs have allelic exclusion?
B cell light and heavy chains
TCR b chain
Self MHC restriction
T cells only recognize antigens displayed by MHC molecules that the T cell encountered during maturation in the thymus (and thus sees self)
CD1
- Class I like non classical MHC molecule
- Bind and display lipids (instead of peptides) to certain types of T cells, particularly NKT
MHC Class I
- Expressed on most nucleated cells
- Displays peptides to and recognized by CD8+ T cells
- Composed of 3 genes: HLA- A, HLA- B- HLA-C
- Increased expression can be induced by interferon A, B, G and TNF
- Composed of alpha chain (a3 is conserved among all class I MHC) with beta 2 microglobulin unit
- Accomodates peptides 8-11 residues long
- A3 binds CD8
MHC class II
- Normally expressed only on DCs, B cells, macrophages and a few other types
- 3 genes HLA DP, DQ, and DR
- Interferon gamma is principal cytokine
- Composed of alpha and beta chain
- B2 is invariant and binds CD4
Where are the mature T cells?
Thymic medulla
Most effective for activating naive T cells
DCs
Most effective at activating effector T cells
B cells and macrophages
Which uses proteosome and TAP?
MHC CLASS I (cytosolic and nuclear protein antigens)
What is the process for peptide MHC class II production?
Protein antigens are captured from the extracellular environment–> internalized into endosomes by specialized APCs–> Degradative enzymes in endosomes and lysosomes generate peptides–> MHC II are synthesized int he ER and transported to same endosomes with the invariant chain–> In the endosomal vesicle, invariant chain is degraded, leaving 24 amino acid remnant called CLIP–> CLIP is removed by HLA-DM–> MHC class II is stabilzed and bound to peptide
TCR components
- Variable domain
- Hydrophobic transmembrane region
- Constant domain
- Short cytoplasmic region
What area recognizes peptide MHC complexes?
V region, specifically concentrated
What do T cells require for transition to effector cells?
- First signal is response by the TCR to MHC and peptide on an APC (foreight signal)
- Second signal is costim ligand induced on APC by microbes (danger signal)
CD28
- Recognized and binds B7 proteins on activated APCs
CTLA-4
- Inhibitory receptor of the CD28 family
- Also bind B7
LFA-1
- Binds ICAM-1 on APCs and endothelium and functions to help cell adhesion
CD44
- Binds hyaluronan, involved in leukocyte adhesion to endothelial cells and ECM
CD45
- Tyrosine phosphatase that regulates T and B cell activation
