Chapter Three Receptors And Signaling : B And T-cell Receptors Flashcards
(104 cards)
Antigens
Foreign molecules that signal the presence of no self entities to immune system
Receptor protein
One of major routes by which a cell interprets its surroundings is through the binding of signaling molecules, or ligands, to these proteins
Cytokines
Small molecules that communicate among various populations of immune cells
Chemokines
Specialized cytokines that induce chemo-attraction or -repulsion
Cellular signal
Any event that instructs the cell to change its metabolic or proliferative state
How are signals usually generated
By the binding of a ligand to a complementary cell-bound receptor
What types of ligands are there
Soluble molecule, or peptide, carbohydrate or lipid
How does ligand travel
Through bloodstream or lymphatics
What kind of molecular change can a ligand induce in a receptor
Conformation change
Dimerization or clustering
Change in location in membrane
Covalent modification
What do ligand caused receptor alterations set off
Cascades of intracellular events like activation of enzymes, changes in intracellular location of important molecules
What is usual end result of cellular signaling
Change in transcriptional program of target cell
Hoe does ligand bind to receptor
By noncovalent chemical linkages
Association constant
The ratio of k_1/k_-1, or association rate constant/dissociation rate constant. A measure of affinity of the receptor ligand pair. The relationship between the concentration of reaction product and the product of the concentration of reactants. (Ka). The higher the Ka, the higher the affinity of the interaction.
Dissociation constant, Kd
Reciprocal of association constant. The lower the Ke, the higher the affinity of the interaction.
What are multi alert receptors
They have more than one ligand binding site per molecule
What is the benefit of multivalency
Noncovalent binding interactions are inherently reversible. The ligand spends some of its time on receptor and some of its time off. When more than one binding site is involved, it is less likely that all of the receptor sites will be simultaneously in the off state so that ligand is released.
Avidity
Overall strength of the collective binding interactions that occur during multi alert binding. This can be accomplished with a molecule with multiple binding sites or a receptor that can create a cluster in membrane,
How do we measure affinity of receptor-ligand interactions
Techniques such as equilibrium dialysis or surface plasmon resonance.
Why is it important that receptors are in low affinity form and are expressed on as needed basis
By waiting before expressing high affinity cytokines receptors, lymphocyte conserves energy and prevents accidental initiation immune response to an irrelevant gene,
How are cytokines released exactly where they are needed
Antigen receptor signaling can induce redistribution of the microtubules organizing center (MTOC) within the activated T cell. This causes redistribution of secretory organelles within th T cell cytoplasm, so that cytokines made by the T cell are secreted in the direction of thr T cell receptor, which in in turn is binding to the antigen-presenting cell
Vectorial redistribution of the secretory apparatus
Process that helps cytokines be secreted directly into space between. Activated T cell and antigen presenting cell.
Where are cytokines most concentrated
At cellular interfaces. So, where two cells meet.
Signal transduction
Molecular route by which a ligand receptor interaction is translated into a biochemical change within an affected cell.
Upstream components of a signaling pathway
Components closest to the receptor
