Term
| What are the four stages of the immune response? |
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Definition
1. Lag phase
2. Exponential phase
3. Steady state phase
4. Decline phase |
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Term
| How long does it take to reach protective levels of immunity? |
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Definition
| 1-3 weeks. This is a longer length of time than the immune response, because it takes time for memory cells to proliferate. |
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Term
| Define the lag phase of the immune response |
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Definition
3 - 14 day period of cell proliferation and differentiation before antibody appears
Varies with such factors as the antigen, dose, route of administration, and the individual patient |
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Term
| Define the exponential phase of the immune response |
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Definition
| 4 - 10 days when rate of antibody biosynthesis exceeds rate of catabolism |
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Term
| Define the steady state phase of the immune response |
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Definition
| Rate of antibody biosynthesis and catabolism are approximately equal |
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Term
| In the immune response, which antibodies respond in greatest numbers first? Which respond second? |
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Definition
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Term
| How do antibody levels change from the primary to secondary immune response? |
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Definition
| Total Ab levels are much higher. IgM levels stay about the same, but there is a much greater IgG response because IgG are from memory cells and have greater binding affinity. |
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Term
| Define the decline phase of the immune response |
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Definition
| Antibody biosynthesis has essentially ceased and catabolism occurs. |
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Term
| What two factors does the duration of effective immunity depend on? |
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Definition
1. The amount of antibody formed (ie, first order declined), and to a lesser extent,
2. Efficacy of the antibody |
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Term
| Define secondary immune response |
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Definition
Subsequent exposure to the same antigen. The clones of specific immunogen-reactive cells grow after each exposure and the size of this population is the main determinant of the
speed and intensity of any secondary response. |
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Term
| How do the stages of a secondary immune response compare to those of a primary immune response, in regards to time? |
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Definition
1. Lag phase- shorter
2. Exponential phase- steeper
3. Steady state phase- higher
4. Declining phase- longer (due to more Ab formed) |
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Term
| Why will a secondary response not be seen if it is too soon after primary exposure? |
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Definition
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Term
| Why will a secondary response not be seen if it is too long after primary exposure? |
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Definition
Memory is finite and long term
immunity requires repeated immunogenic exposure |
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Term
| What cells allow T cells to form into effector T cells and B cells to form into plasma cells? |
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Definition
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Term
| What are the broad functions of effector T cells in the efferent immune response? |
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Definition
| Lymphokine release and/or cytotoxicity |
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Term
| What are the broad functions of plasma cells in the efferent immune response? |
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Definition
| Antigen-Antibody reactions (precipitation, agglutination, compartment-fixation, opsonization, virus neutralization |
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Term
| List the four basic steps of the afferent immune response |
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Definition
1. Antigen capture by general APC (ex. dendritic cell)
2. Antigen processing
3. Antigen presentation via class II MHC to specific TH cell receptor
4. TH cell activation |
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Term
| Once a TH cell is activated, what three things can it do in the efferent immune response? |
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Definition
1. Activate a B cell
2. Become a memory TH cell
3. Activate a cytotoxic T cell via IL-2 receptor |
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Term
| Once a cytotoxic T cell is activated, what can it do in the efferent immune response? |
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Definition
1. Become a memory Tc cell
2. Kill infected cells, which present antigen via a class I MHC |
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Term
| Once a B cell is activated, what can it do in the efferent immune response? |
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Definition
1. Undergo differentiation to a plasma cell
2. Undergo proliferation to a memory B cell |
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Term
Where are MHC class I receptors located?
Where are MHC class II receptors located? |
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Definition
MHC class I receptors (CD8): cytotoxic T cells
MHC class II receptors (CD4): helper T cells |
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Term
| Give an example of positive selection (in the immune response) |
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Definition
| Immunogen stimulation of lymphocytes is an example of positive selection that results in the proliferation of the cells. |
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Term
| Define negative selection (in the immune response) |
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Definition
| Immunogen stimulation of lymphocytes under some special circumstances results in death of the cell. This is of greatest importance in two areas which will be discussed in more detail later. |
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Term
| Why is negative selection (cell death) in the immune response so important? |
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Definition
1. It limits the extent of a normal immune response
2. Discrimination of self and preventing attack of the host by autoreactive clones of cells |
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Term
|
Definition
Physiologic or programmed cell death
A physiologic signal programs the cell to die rather than the cell being killed by lysis, a metabolic toxin, etc. |
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Term
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Definition
| A substance capable of inducing an immune response in a susceptible animal and reacting with the products of that response. |
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Term
| What three things can an immunogen refer to? |
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Definition
1. Immunogenic substance
2. Immunogenic compound
3. Epitope |
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Term
| Define immunogenic substance |
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Definition
| Substance that contains one or more immunogenic compounds; e.g., microorganism, pollen |
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Term
| Define immunogenic compound |
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Definition
| A single molecule that may have more than one specificity |
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Term
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Definition
A part of an immunogenic molecule that determines specificity and binds with an antibody or gives rise to the MHC-binding peptide that is recognized by the T-cell receptor.
(aka immunogenic determinant, antigenic determinant) |
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Term
| Are all immunogens antigens? |
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Definition
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Term
| Are all antigens immunogens? |
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Definition
|
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Term
|
Definition
| A substance that can react with immune effectors (Ab or T-cell receptors) |
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Term
| Define complete immunogen |
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Definition
Complete Immunogens are capable of inducing an immune response themselves.
These are usually proteins but may be polysaccharides.
1. The term immunogen implies that a substance is "complete" |
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Term
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Definition
| Haptens (Partial Immunogens) are not capable by themselves of inducing an immune response but may do so when covalently bound to a suitable carrier compound, usually a protein. |
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Term
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Definition
| Virtually any compound with the potential to covalently bind to protein is a possible hapten. This includes most conventional drugs and their metabolites. |
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Term
| Are haptens active during an immune response? |
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Definition
Haptens serve as an epitope (or part of an epitope) and thus determine the specificity of the immune response.
Free haptens, while not inducing an immune response, will often react with the effectors (e.g., antibody) formed in the response. |
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Term
| Why can most drugs cause allergy? |
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Definition
| Because they act as haptens, serving as an epitope on a carrier protein. |
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Term
| Are all haptens proteins? |
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Definition
| No, virtually any chemical class can be a hapten |
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Term
| Give an example of an antigen that is not an immunogen |
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Definition
| A free hapten that is not bound to a carrier, but still interacts with effectors (antibodies) during an immune response |
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Term
| How does penicillin usually become a hapten? |
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Definition
| The lactam ring in penicillin is opened up (the penicilloyl configuration), which is a major antigenic determinant for antibodies and T cells. |
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Term
| How is immunogenicity related to molecular weighr? |
|
Definition
Immunogenicity usually increases with molecular weight
Around 10,000 is threshold, >100,000 is highly immunogenic |
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Term
| List five physical characteristics that can lead to immunogenicity |
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Definition
1. Chemical class (protein)
2. Molecular size (larger)
3. Source (foreign)
4. Chemical complexity
5. Epitopes |
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Term
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Definition
| The absence of an immune response to something that is immunogenic in others |
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Term
Variation in 1-2 amino acids away from the active
site of an enzyme or hormone generally has very little effect on the biological activity of a protein. Can it have a major effect on immunogenicity? |
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Definition
| Yes, even though it might not even have a different structure |
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Term
| If a single amino acid such as (Gly-Gly-Gly-Gly) is repeated in sequency, is it likely to be immunogenic? |
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Definition
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|
Term
| Which are more likely to be immunogenic, aromatic or aliphatic amino acids? |
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Definition
|
|
Term
| Describe the chemical bond between antigen and antibody |
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Definition
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Term
| Describe the valency and specificity of immunogens |
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Definition
Multivalent and multispecific
Important because we don't need to respond to every epitope- just a few is enough |
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Term
| How large are most epitopes? |
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Definition
3-20 amino acid or monosaccharide units in size
It is interesting that this is a similar size to most conventional drugs (MW 250-1000) |
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Term
| Define cross-antigenicity |
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Definition
| The level of specificity in immune reactions is very high but nonetheless relative. Epitopes of similar size, shape and charge may crossreact |
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Term
| Is a native epitope (in a macromolecule) identical to the same free epitope? |
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Definition
| No, a free epitope may or may not react with antibodies induced by the complete immunogen |
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Term
| What is the key difference between B cell immunogens and T cell immunogens? |
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Definition
B cell immunogens react directly with the B cells
T cell immunogens must be processed which includes hydrolysis to smaller fragments |
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Term
|
Definition
| An epitope comprised of a linear sequence of amino acid or sugar residues (3-20 units) in a macromolecule |
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Term
| Define discontinuous (conformational) epitope |
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Definition
An epitope created by individual units occupying a number of non-adjacent sites in the macromolecule that have been brought into proximity by the conformation of the molecule
Can be disrupted by protein denaturation |
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Term
|
Definition
A way to compare two epitopes within the same immunogen molecule.
Factors that determine immunodominance include position within chain, conformation, hydrophilicity, steric structure |
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Term
| About how many epitopes can an individual respond to? |
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Definition
| 10^6 - 10^8 different epitopes |
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Term
| Why does the typical immunogen have to be multivalent to generate a response? |
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Definition
The normal antibody response requires at least two determinants—one to trigger a T cell response and the second the B cell response.
(The usual antibody response is said to be thymic dependent and little or no antibody will be formed in the absence of helper function.) |
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Term
| Define a thymic-independent antibody response |
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Definition
| An atypical antibody response consisting mainly of IgM and no immunologic memory. |
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