Antigens and the Major Histocompatibility Complex Flashcards
macromolecules capable of triggering an
adaptive immune response by inducing the formation of antibodies or sensitized T cells in an immunocompetent host
immunogens
a substance that reacts with antibody or sensitized
T cells but may not be able to evoke an immune response
antigen
all immunogens are antigens but not all antigens are immunogens
true
what are the biological properties of an individual that can influence immune response
age, overall health, dose, route of inoculation, genetic opacity
the larger the amount of an immunogen one is exposed to, the greater the immune response
true
older individuals are more likely to have a decreased response to antigenic stimulation, neonates do not fully respond to immunogens, because their immune systems are not
completely developed
age
individuals who are malnourished, fatigued, or stressed are less likely to mount a successful immune response
overall health
a threshold dose, 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
dose
include intravenous (into a vein), intradermal (into the skin), subcutaneous (beneath the skin), and oral administration (lecules)
route of inoculation
linked to the MHC and to the receptors
generated during T and B lymphocyte development
genetic capacity
a system of genes that code for cell-surface molecules that play an important role in antigen recognition
major histocompatibility complex (MHC)
ability of an immunogen to stimulate a host response
immunogenicity
what should be the molecular weight of immunogen to be recognized the immune system
10,000 daltons
best immunogens typically have a molecular weight of over _____?
100,000 daltons
the rule of thumb in macromolecular size (trait of immunogen) is that the GREATER the MOLECULAR WEIGHT, the MORE POTENT the molecule is as an antigen
true (macromolecular size of immunogen - a trait of immunogen)
all immunogens share foreigness
true
substances recognized as nonself are immunogenic
true
enumerate the traits of immunogens
(1) macromolecular size (2) chemical composition and molecular complexity (3) foreignness (4) ability to be processed and presented with MHC
these are the best immunogens
proteins and polysaccharides
immunogens that are somewhat less immunogenic than protein
carbohydrates
carbohydrates immunogens could be in what forms
glycolipids and glycoproteins
A, B, and H blood group antigens are?
glycolipids
Rh and Lewis antigens are?
glycoproteins
not immunogenic by themselves, although a response can be generated when they are attached to a suitable carrier molecule
pure nucleic acids and lipids
being able to distinguish between self and non-self, and those substances recognized as non-self are immunogenic
foreignness
involves enzymatic digestion to create small peptides or pieces that can be complexed to MHC molecules to present to responsive lymphocytes
ability to be processed and presented with MHC
molecules
determinant site
epitope
molecular shapes or configurations that are recognized by B or T cells
epitope
may be repeating copies, or they may have differing specificities; linear or conformational
epitope
surface antibody on B cells MAY REACT WITH BOTH LINEAR OR CONFORMATIONAL EPITOPES present on the surface of an immunogen
epitope recognition by B cells
recognize an epitope only as a PART OF COMPLEX FORMED WITH MHC proteins on the surface of an antigen-presenting cell (APC)
epitope recognition by T cells
epitopes recognized by B cells may differ from those recognized by T cells
true
anything that is capable of cross-;inking surface immunoglobulin molecules is able to trigger B-cell activation
true
non-immunogenic materials that when combined with a carrier, create new antigenic determinants
haptens
may be complexed artificially with carrier molecules in a laboratory setting, or this may occur naturally within a host and set off an immune response
haptens
once antibody production is initiated, the hapten is capable of reaction with antibody even when the hapten is not complexed to a carrier molecule
true
a substance administered with an immunogen that increases the immune response
adjuvants
acts by producing a local inflammatory response that attracts a large number of immune system cells to the injection site
adjuvants
the only adjuvants approved for clinical use
in the United States used to complex with the
immunogen to increase its size and to prevent a rapid escape from the tissues; injected into the muscle to work
aluminum salts
a vaccine that uses aluminum salts as adjuvants
hepatitis B vaccine
adjuvants enhance the immune response by (1) PROLONGING existence of immunogen in the area (2) INCREASING the effective SIZE of the immunogen (3) INCREASING the NUMBER of macrophages involved in antigen processing
true
antigens that belong to the host; do not evoke an immune response under normal circumstances
autoantigens
antigens from other members of the host’s species; capable of eliciting an immune response; important to consider in tissue transplantation and in blood transfusions
alloantigens
antigens from other species, such as other
animals, plants, or microorganisms
heteroantigens
heteroantigens that exist in unrelated plants or animals but are either identical or closely related in structure so that antibody to one will cross-react with an antigen of the other
heterophile
major histocompatibility complex molecules are formerly known as?
human leukocyte antigens (HLA)
they determine whether transplanted tissue is histocompatible and thus accepted or recognized as foreign and rejected
MHC molecules
its main function is to bring antigen to the cell surface for recognition by T cells because T-cell activation will occur only when antigen is combined with it
MHC molecules
genes controlling expression of MHC molecules are actually a system of genes known as?
major histocompatibility complex (MHC)
genes coding for the MHC molecules in humans are found on the short arm of? and are divide into ____ categories or classes.
chromosome 6 ; three (Class I, II, and III)
molecules are coded for at three different
locations or loci, termed A, B, and C
class I
genes are situated in the D region and there
are several different loci, known as DR, DQ, and DP
class II
coded between the class I and class II regions
on chromosome 6
class III
codes for complement proteins (C4A, C4B, C2 and B complement) and cytokines such as TNF
class III
expressed on ALL NUCLEATED CELLS
structure of class I MHC molecules
highest on lymphocytes and low or undetected on liver hepatocytes, neural cells, muscle cells, and sperm
structure of class I MHC molecules
a structure of class I MHC molecules that has a molecular weight of 45,000
alpha chain
a light chain associated with alpha chain that has a molecular weight of 12,000 (structure of class I)
beta-2-microglobulin
structure of class I MHC molecules that REACTS WITH CD8 on cytotoxic T cells
alpha-3 region
found primarily on antigen-presenting cells (APC) which include B lymphocytes, monocytes, macrophages, and dendritic cells
structure of class II MHC molecules
expressed at the highest level, as it accounts for about one-half of all the class II molecules on a particular cell ; this gene is the most highly polymorphic, as 18 different alleles are known at this time (structure of class II)
DR
both the chain, with a molecular weight of __________, and the chain, with a molecular weight of ____________, are ANCHORED TO THE CELL MEMBRANE (structure of class II)
33,000 ; 27,000
what is the role of MHC class I and II
to bind peptides within cells and transport them to the plasma membrane where T cells can recognize them in the antigen presentation
role of MHC class I and II is to bind peptides within cells and transport them to the plasma
membrane, where T cells can recognize them in the phenomenon known as
antigen presentation
mainly present peptides that have been synthesized within the cell to CD8 (cytotoxic) T cells
class I
the watchdogs of viral, tumor, and certain parasitic antigens that are synthesized within the cell
class I
Display of hundreds of class I molecules complexed to antigen allows CD8+ T cells to continuously check cell surfaces for the presence of non-self antigens. If it recognizes an antigen as being foreign, the CD8+T cell produces _______ that causes lysis of the entire cell.
cytokines
present antigen to CD4 (helper) T cells
class II
mainly binds exogenous proteins - those taken into the cell from the outside and degraded
class II
stimulate CD4 T cells in the case of bacterial infections or the presence of other material that is endocytosed by the cell
class II
on the cell surface, class II molecules are responsible for forming a _________ that occurs between antigen, class II molecule, and an appropriate T-cell receptor. if binding occurs with a T-cell receptor on a CD4+ T cell, the helper T cell recruits and triggers a _______ response resulting in ________ formation
trimolecular complex ; B cell ; antibody
