First Aid: T and B cells Flashcards
What are the positive and negative selective factors for T cells?
positive selection happens in the thymic cortex: only those cells capable of binding surface self MHC molecules survive
negative selection happens in the medulla: T cells expressing receptors with a high affinity for self antigens undergo apoptosis
What factors promote development to Th1 vs. Th2 cells?
CD4 + cells go to Th1 when exposed to IL-12
they go to Th2 if exposed to IL-4.
Remember, Th1 cells make IL-2 and IFN-gamma; Th2 cells make IL-4,5, and 13.
What do regulatory t cells do? What do they produce? How are they activated?
help maintain immune tolerance by suppressing CD4 and CD8 effector functions. When activated, they make anti-inflammatory cytokines like IL-10 and TGF-beta
they are activated by TGF-beta.
What does the Fab portion of the the antibody do? What does it determine?
Fab binds antigen
determines idiotype
What does the Fc portion of the antibody do? What does it determine? Why is the c helpful for remembering things?
Fc is constant, at the carboxy terminal, complement binding, carbohydrate side chains. determines isotype (IgM, IgD).
What are 3 functions of antibodies?
opsonization (promotes phagocytosis), neutralization, and complement activation
How is antibody diversity generated?
- Random recombination of VJ (light chain) and VDJ (heavy chain) genes in primary lymphoid tissue
- Random combination of heavy chains and light chains
- Somatic hypermutation following antigen stimulation
- Addition of nucleotides to DNA during recombination by terminal deoxynucleotidyl tranferase
Which antibody isotypes fix complement? Which antibody types cross the placenta?
Complement: IgG, IgM. Placenta: IgG
What should I know about IgA structure? How does IgA cross epithelial cells?
prevents attachment of viruses and bacteria to mucus membranes. Monomer in circulation or dimer when secreted. Crosses epithelial cells by transcytosis.
What is the most abundant antibody? What antibody am I most likely to find in blood?
overall, IgA is most abundant ab. but, it is largely released in secretions, so IgG is most abundant in blood.
What is the structure of IgM?
monomer on the B cell; pentamer when secreted. pentamer shape allows it to trap things.
What are the functions of IgE?
binds mast cells and basophils. cross-links when exposed to allergen. mediates immunity to worms by activating eosinophils.
What factors induce acute phase reactants?
IL-1, IL-6, TFN-alpha, IFN gamma
What are some upregulated acute phase reactants?
serum amyloid A, C-reactive protein, ferritin, fibrinogen, and hepcidin.
serum amyloid can cause amyloidosis if it is elevated for a long time. CRP is an opsonin and fixes complement. it is used to measure inflammation. Ferritin binds and sequesters iron; hepcidin prevents release of iron bound by ferritin. Fibrinogen is a coag factor that promotes endothelial repair.
What are some proteins that are down regulated in inflammation?
albumin (conserves aas), and transferrin (internalized by macrophages to sequester iron).
