Antigens Flashcards
The immune response of lymphocytes is triggered by materials called_______
immunogens
macromolecules capable of triggering an adaptive immune response by inducing the formation of antibodies or sensitized T cells in an immuno-competent host.
Immunogens
Immunogens can then specifically react with such…
antibodies or sensitized T cells
The term____ refers to a substance that reacts with antibody or sensitized T cells but may not be able to evoke an immune response in the first place.
antigen
older individuals are…
At the other end of the age scale, neonates…
more likely to have a decreased response to antigenic stimulation.
do not fully respond to immunogens, because their immune systems are not completely developed.
________plays a role, as individuals who are malnourished, fatigued, or stressed are less likely to mount a successful immune response.
Overall health
There appears to be a _______for each individual immunogen.
This allows the innate immune response to take care of small amounts of pathogens and leave the adaptive response for pathogens that are present in large numbers.
threshold dose
Generally, the larger the dose of an immungen one is exposed to, the______ the immune response is.
However, very large doses can result in________, a phenomenon that is not well understood. It is possible that memory cells become overwhelmed and therefore nonresponsive.’
greater
T- and B-cell tolerance
The actual amount of immunogen needed to generate an immune response differs with the…
route of inoculation.
route of inoculation
Such routes include (4) Where the immunogen enters the body determines which cell populations will be involved in the response and how much is needed to trigger a response.
intravenous (into a vein)
intradermal (into the skin)
subcutaneous beneath the skin)
oral administration
________may be involved that allows individuals to respond to particular immunogens.
This predisposition is linked to the MHC and to the receptors generated during T and B lymphocyte development.
genetic predisposition
In general, the ability of an immunogen to stimulate a host response depends on the following characteristics:
TRAITS OF IMMUNOGENS
(1) macromolecular size
(2) chemical composition and molecular complexity
(3) foreignness
(4) the ability to be processed and presented with MHC molecules
Usually an immunogen must have a molecular weight of at least______ to be recognized by the immune system, and the best immunogens typically have a molecular weight of_______
However, there are exceptions, because a few substances with a molecular weight of ______have been known to induce an immune response.
10,000
over 100,000 daltons
less than 1000
The rule of thumb is that the greater the molecular weight…
the more potent the molecule is as an immunogen
Immunogenicity is also determined by a substance’s chemical composition and molecular complexity.
_______are the best immunogens.
Proteins and polysaccharides
are powerful immunogens, because they are made up of a variety of units known as amino acids.
Proteins
Because of the variations in subunits,_______ may have an enormous variety of three-dimensional shapes.
B cells recognize structures that project from the external surfaces of macromolecules, and the more complexity or branching there is, the easier it is for B cells to respond.
proteins
_______ have epitopes that also stimulate T cells, which is essential to generating T-cell help in antibody pro-duction.
In contrast,______ such as nylon or Teflon are made up of a few simple repeating units with no bending or folding within the molecule, and these materials are_______. For this reason, they are used in making artificial heart valves, elbow replacements, and other medical appliances.
Proteins
synthetic polymers; nonimmunogenic
are somewhat less immunogenic than protein, because the units of sugars are more limited than the number of amino acids in protein.
Carbohydrates
As immunogens, carbohydrates most often occur in the form of____ or_____
Many of the blood group antigens are comprised of such carbohydrate complexes.
For example, the A, B, and H blood group antigens are_______, and the Rh and Lewis antigens are________.’
glycolipids or glycoproteins
glycolipids
glycoproteins
_________ and________ are not immunogenic by themselves, although a response can be generated when they are attached to a suitable carrier molecule.
This is the case for autoantibodies to DNA that are formed in systemic lupus erythematosus.
These autoantibodies are actually stimulated by a DNA-protein complex rather than by DNA itself.
Pure nucleic acids and lipids
Another characteristic that all immunogens share is________.
The immune system is normally able to distinguish between self and nonself, and those substances recognized as nonself are______.
foreignness
immunogenic
Any lymphocyte capable of reacting with self-antigen is normally______.
Typically, the more distant_____ the source of the immunogen is from the host, the better it is as a stimulus.
For example, plant protein is a better immuno-gen for an animal than is material from a related animal.
Occasionally, however, autoantibodies, or antibodies to self-antigens, exist.
eliminated
taxonomically
F a substance to elicit an immune response, it must be subject to______, which involes enzymatic digestion to create small peptides or pieces that can be complexed to MHC molecules to present to responsive lymphocytes.
antigen processing
If a macromolecule can’t be degraded and presented with MHC molecules, then it would be a_______.
The particular MHC molecules produced also determine responsiveness to individual antigens.
poor immunogen
Immunogens:
Macromolecules that induce the formation of antibodies or sensitized T cells in an immunocompetent host.
• Antigens:
Substances that react with antibodies or sensitized T cells but may not evoke an immune response initially.
Rule of thumb in immunogen-antigen
“All Immunogens are Antigens, but not all antigens are immunogens.”
Examples of immunogens
Bacteria
Viruses
Fungi
Parasites
Example of antigens
RBCs
______ regions of antibodies will bind with the antigens
Fab region
PAMPs are…
Epitopes
Are small molecules that are antigenic but not immunogenic by themselves.
HAPTEN
HAPTEN
are small molecules that
are antigenic but not immunogenic by themselves.
Why are haptens not consisdered as immunogens/ will not elicit immune response? What do they need, to be considered as an immunogens?
They are so small that out body wouldn’t elicit an immune response.
Low molecular weight particles that can bind to an antibody but must be attached to a macromolecule as a carrier to stimulate a specific immune response
Once it bind with a carrier proteins, it give it an impression that they are bigger thus the body will now elicit an immune response
Haptens are nonimmunogenic materials that, when combined with a carrier, create new antigenic determinants that is recognized by the body as immunogenic.
What will happen in the next exposure to a hapten?
Once the body starts making antibodies, a hapten (a small molecule) can react with these antibodies even if it’s not attached to a larger carrier molecule. However, because the hapten is so small and has only one binding site, it can’t link multiple antibodies together. This means it won’t cause clumping or precipitating reactions, which require cross-linking between antibodies.
______indicates the presence of that particular antigen.
Agglutination
is the process by which particulate antigens such as cells aggregate to form larger complexes when a specific antibody is present.
Agglutination