Chapter 3 Antigen Capture and Presentation to Lymphocytes Flashcards
What can antibodies recognize?
antigens, lipids, nucleic acids, and other types of molecules
What happens when naive T cells are activated?
clonal expansion and differentiation into effector T cells
What happens when effector T cells are activated?
- activation of macrophages (cell-mediated immunity)
- B cell activation and antibody production (humoral immunity)
What activates a naive T cell?
dendritic cell
- though a costimulator B7 and CD28
What allows for a naive T cell to get activated?
Costimulator (B7)
CD28
What kills a virus infected cell?
CD8+ T cells
Where do dendritic cell-associated antigens go?
- lymph nodes
- circulation and spleen
What happens to the dendritic cell-associated antigens in the lymph node?
lymph node collects antigens from tissue
What happens to the dendritic cell-associated antigens in the spleen?
blood-borne antigens are captured by antigen-presenting cells in the spleen
What are the major cytokines produced from dendritic cells?
- TNF
- IL-6
- IL-12
- Type 1 interferons
What are the toll-like receptors for dendritic cells?
-TLR 4, 5, 8
Why are costimulators important?
Costimulators are important for antigen presentation to by dendritic cells activate naïve T cells
What is the major costimulator for naive T cell activation via dendritic cells?
B7
Capture and presentation of antigens by _________ cells
dendritic
- also macrophages and B lymphocytes
What is a MHC (major histocompatibility complex)?
MHC are expressed on antigen-presenting cells and function to display peptides derived from protein antigens.
Does each T Cell recognize every residue of a peptide?
No, the receptor of every T cell recognizes some residues of the peptide and some (polymorphic) residues of the MHC molecule.
What are the polymorphic regions of the class I MHC?
a1 and a2
What does a3 bind to on the T cell in class I MHC?
CD8 T cell co-receptor
CD8+ T cells can only respond to antigen presented by MHC class __ molecules
class I
CD4+ T cells can only respond to antigen presented by MHC class __ molecules
class II
What are the polymorphic regions of the class II MHC?
a1 and a2
a2 and B2 bind to what on the T cell in class II MHC?
CD4 T cell co-receptor
Peptide-binding cleft for peptides ______ aa long in Class II MHC
10-30
Peptide-binding cleft for peptides ______ aa long in Class I MHC
8-9
What genes are the most polymorphic genes in the genome?
Class I and class II MHC genes
____________ expression of class I and class II MHC alleles inherited from parents
Codominant
Professional antigen presenting cells such as dentrictic cells, macrophages, and B cells activate what type of T cell?
CD4+ helper T cell
All nucleated cells can activate what type of T cell?
CD8+ T cell (can kill any virus infected cell)
What are the characteristics of MHC molecules?
- broad specificity
- displays one peptide at a time
- bind only peptides
- peptides are aquired druing intracellular assembly
- stable surface expression of MHC molecule
- very slow off-rate
Class II MHC displays peptides from what cellular compartment?
peptide from endocytic vesicle
Class I MHC displays peptides from what cellular compartment?
cytosolic peptide transported into ER
CD8+ Cytotoxic T cells (CTLs) recognize what kind of antigen presented by MHC class I molecules on an infected cell?
endogenous (cytosolic) antigen
What is the class I MHC pathway of processing cytosolic antigens?
- production of proteins in cytosol (some of them are viral proteins)
- proteolytic degradation of proteins
- transport of peptides from cytosol to ER
- assembly of peptide-class I complexes in ER
- surface expression of peptide-class I complexes (could have viral proteins on it that CD8+ cells would recognize)
CD4+ Helper T cells recognize what type of antigen presented by MHC class II molecules on a professional antigen presenting cell
exogenous antigen
What is the class II MHC pathway of processing internalized vesicular antigens?
- uptake of extracellular proteins
- processing of internalized proteins in endosomal/lysosomal vesicles
- biosynthesis and transport of class II MHC molecules to endosomes
- association of processed peptides to class II MHC molecules in vesicles
- expression of peptide-MHC complexes on cell surface (some could have pathogen proteins and would be recognized by CD4+ helper T cell)
What do dentritic cells use that allows presentation of microbial antigens from infected cells?
Class I MHC-restricted cross-presentation
What happens when macrophages are activated?
killing of phagocytosed microbe
What happens when B cell antibody secretion occurs?
antibodies bind to antigens
What are the 2 ways CD4+ helper T cells use the Class II MHC pathway?
activates macrophages
activates B cell antibody secretion
