Term
| what is a protein domain? |
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Definition
| a protein domain is an amino acid sequence in a peptide that defines a region that regularly folds the same way and performs a predictable function, such as the catalytic site of an enzyme |
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Term
| what is an immunoglobulin domain? |
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Definition
an immunoglobulin domain is an amino acid sequence in an antibody peptide that always folds into the same functional structure
immunoglobulin domains are the heavy chain and light chain variable and constant |
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Term
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Definition
a cytokine is a protein that is made by cells of the immune system
some cytokines can boost the immune response and others can suppress it |
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Term
| what is the difference between the variable domains and the constant domains? |
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Definition
| constant domains are coded by the inherited genome, variable domains coded by recombined DNA |
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Term
| which domains bind to antigen and why? |
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Definition
| the heavy and light chain variable domains bind antigen because their sequence was selected out by the B-cell repertoire |
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Term
| what does the structure of the constant domain tell you? |
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Definition
| the constant domain varies between Ig classes; tell you which type of antibody it is |
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Term
| what function does the Fc region of an antibody have? |
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Definition
| Fc fragment mediates effector activity |
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Term
| what is an effector molecule of the immune system? |
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Definition
| effector molecules bind to Fc and cause some effector process to happen, such as complement-mediated lysis, phagocytosis, and cell mediated cytotoxicity |
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Term
| what are the 3 principal modes of action of therapeutic antibodies? |
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Definition
| blocking ligand receptor interactions, targeting cells for destruction or something else, acting as signaling agonists |
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Term
| what are the 2 ways that blocking antibodies can interrupt cytokine signaling? |
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Definition
| block by binding ligand or block by binding receptor |
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Term
| what sorts of signaling effects can antibodies have? |
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Definition
| crosslinking receptors to activate cell division or other responses, including apoptosis |
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Term
| what is complement-dependent cytotoxicity? |
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Definition
| after antibody binding via Fab sites, complement factors attach to Fc and form the membrane attack complex to form a hole in the target cell |
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Term
| which antibody classes are involved in CDC? |
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Definition
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Term
| what effector molecules are involved in CDC? |
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Definition
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Term
| what 3 problems are seen when mouse monoclonal antibodies are used as therapeutic or diagnostic agents in humans? |
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Definition
short half life
failure to trigger effector function
human anti-mouse antibodies |
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Term
| what approach was taken to fix these problems? |
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Definition
| genetic engineering approach to make chimeric antibodies that are partially human sequence and less immunogenetic |
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Term
| what is a chimeric antibody? |
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Definition
| a genetically engineered antibody with human constant domains and mouse variable domains |
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Term
| what advantages do chimeric antibodies have? |
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Definition
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Term
| what is CDR (complementarity-determining region) grafting |
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Definition
| complementarity-determining region grafting is an attempt to minimize the mouse sequence by only cloning the mouse CDR sequence into a human variable domain |
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Term
| what 3 developments have lead to the possibility of making fully human antibodies by genetic engineering? |
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Definition
discovery of human variable region genes
successful expression of them in E. coli
invention of phage display method |
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Term
| if you were determined to use mice to make fully human monoclonal antibodies, what would you have to do to the mice? |
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Definition
| exchange natural mouse immunoglobulin genes for the human genes |
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Term
| what is serum therapy and when was it used? |
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Definition
serum therapy is the IV use of serum from a patient who is assumed to have immunity to the infection disease of the patient
primarily used before the era of antibiotics |
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Term
| is serum therapy still used, and if so, for what purpose? |
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Definition
| today serum therapy is only used for emergencies such as acute lethal toxin or virus exposure such as rabies, botulism. |
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Term
| what is post-exposure prophylaxis? |
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Definition
| prevention of infection after known exposure to the agent |
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Term
| what are the 5 immunoglobulin classes? |
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Definition
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Term
| what class is the first produced in a primary immune response? |
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Definition
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Term
| which class is involved in histamine release? |
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Definition
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Term
| which class is most abundant in serum? |
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Definition
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Term
| which class protects the fetus? |
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Definition
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Term
| what are the 2 main techniques used to make fully human monoclonal antibodies today? |
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Definition
transgenic mice and phage display
the in vivo process of the production of fully human monoclonal antibodies is based on the immunization of a transgenic mouse
the mouse has been genetically engineered and bred for the expression of human immunoglobulins
the B cells harvested after immunization can be immortalized by fusion with a myeloma cell line, as in traditional hybridoma technology
in phage display, the variable genes encoding the antibody variable domains are fused to genes encoding bacteriophage coat proteins
the system is highly effective and is used to isolate single chain Fv or Fab fragments with specificity to almost any kind of antigen
the plasmid encoding and variable genes is packaged within the viral capsid and the expressed antibody is presented on the bacteriophage surface |
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Term
| what is the most effective way of making a drug using monoclonal antibodies to treat viral infections |
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Definition
making an artificial polyclonal mixture of monoclonal antibodies
the efficacy of monoclonal antibodies for infectious disease can be increased when a polyclonal passive human serum therapy is mimicked - that is, when a pool of highly specific and high affinity monoclonal antibodies are administered
the overall outcome might be effective protection due to the combination of the blocking, neutralizing, and eliminating effect of human antibodies
human monoclonal antibodies against hepatitis B virus:
the 2 monoclonal antibodies were combined with lamivududine (an antiviral drug that inhibits DNA replication) and showed significant reduction in serum viral titre |
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Term
| which cytokine is associated with rheumatoid arthritis and how? |
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Definition
| TNF-alpha accumulates in joints where it causes inflammation |
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Term
| what are the 2 most frequent general disease indications for approved monoclonal antibodies? |
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Definition
cancer (6)
immune (4)
CV (2)
infectious disease (1) |
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Term
| what is the general purpose of using therapeutic antibodies to treat cancer? |
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Definition
| cause direct or indirect destruction of cancer cell |
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Term
| what are the 2 main targets of these anti-cancer antibodies? |
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Definition
| target the cancer cell or its blood supply |
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Term
how can you use radioactive elements and antibodies together to kill cancer cells
how can you use toxins and antibodies together to kill cancer cells? |
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Definition
| tightly bind a radionuclide or toxin to the antibody without blocking the Fab binding site |
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Term
| what do you need in an antibody in order to kill tumor cells by natural immunoglobulin effector functions? |
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Definition
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Term
| why do antibodies that block VEGF signaling inhibit tumor growth? |
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Definition
| VEGF causes a blood supply to form that nourishes the tumor |
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Term
| are there any approved antibodies that work by this mechanism? |
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Definition
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Term
| what is a naked antibody and how does it differ from other types of therapeutic antibodies? |
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Definition
a plain antibody molecule with nothing attached to it and requires natural Fc-mediated effector function to have a therapeutic effect
naked antibodies do not have a radioisotope or toxin attached to them
the elimination of the target of these antibodies depends entirely on the recruitment of the body's own effector mechanisms, namely complement activation and Fc-receptor dependent responses |
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Term
| when naked antibodies kill cancer cells via effector cell cytotoxicity, how does the killing actually happen? |
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Definition
cytoxic and phagocytic cells bind the Fc region and kill or engult the cancer cell
both trastuzumab and rituximab seen to exert their effects primarily through an Fc receptor dependent mechanism, and both are of the IgG subclass of antibodies and thus bind to all known Fcgamma receptors
these receptors are located in the membrane of various effector cells such as NK cells, neutrophils, monocyte/macrophages, dendritic cells, and B cells
in general, IgG-FcgammaR crosslinking leads to antibody-cell cytotoxicity or phagocytosis of the target cells by the effector cell |
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Term
| what are bispecific antibodies and how could they be used? |
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Definition
| bispecific antibodies have 2 different antigen specificities |
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Term
| what effector cell population would be the best target for bispecific antibodies? |
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Definition
| a cytotoxic effector cell |
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Term
| what adverse side effect of naked antibody therapy is possible and what approach is taken to avoid it? |
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Definition
cytokine storm (cytokine release syndrome)
Fc receptor can be mutated to prevent activation of immune effector cells and cytokine secretion |
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Term
| how can small antibodies lacking the Fc region be used in therapy? |
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Definition
| neutralizing toxins and blocking ligand receptor interactions |
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Term
| which antibody fragments can be used as blocking agents? |
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Definition
Fv (engineered)
Fab (natural or engineered)
Fab2 (natural or engineered)
the variable domains of both the heavy and light chains compose the antigen binding part of the molecule, termed Fv
[image] |
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Term
| what 2 major advantages does the phage library approach have over the traditional monoclonal antibody approach (injecting mice and making hybridomas)? |
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Definition
more screening capacity can give better specificity and affinity
haptens, toxic drugs, and other toxic substances can be used as antigens |
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Term
| what approach in engineering antibodies is taken to increase avidity (combined strength of multiple bond interactions)? |
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Definition
| producing single chain Fv molecules and then grouping them into dimers and trimers |
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Term
| what effect on crosslinking ability does an increase in avidity have? |
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Definition
| increasing avidity increases crosslinking activity |
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Term
| are complete antibody molecules able to penetrate tissues easily |
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Definition
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Term
| what 2 key factors affect the therapeutic efficacy of antibodies |
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Definition
stability (half life)
immunogenicity |
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Term
| what is the pharmacokinetic problems posed by small antibody fragments? |
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Definition
| rapid clearance from the circulation |
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Term
| why do complete antibodies tend to have a long serum half life? |
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Definition
presence of the Fc region allows binding of neonatal Fc receptor that prevents destruction of antibody
the neonatal Fc receptor both transports IgG across the placenta from mother to fetus and protects serum IgG from degradation |
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Term
| what modifications can be made to increase the serum half life of antibodies and their fragments? how does it work? |
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Definition
addition of polyethylene glycol polymers
raises size above kidney filtration threshold and lowers immunogenicity |
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Term
| what 2 immune potentiation properties will the best vaccines for infectious disease have? |
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Definition
| stimulation of both antibody and T cell |
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Term
| what does a "troybody" do and how does it work? |
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Definition
a "troybody" is an antigenic protein that is bound to Fc while Fab targets specific T cells
one strategy for increasing the immune response is to load antibodies with antigenic material in the CDR regions
this stragety is one of several that aim to use the Fc portion of the antibody to load specialized immune cells with antigenic material
in the troybody strategy, the antibodies carry pieces of antigenic material as part of their Fc region and target the specialized immune cells by way of their Fab regions
in all cases, the purpose of the immune cell loading is to activate disease specific helper T cells
troybodies increase such T cell responses more than 10,000 fold compared with administration of the antigenic material in free form |
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Term
| what other way could you deliver antigen to immune effector cells |
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Definition
| attach antigen to another part of the antibody molecule to allow Fc-mediated uptake |
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