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63 Cards in this Set

  • Front
  • Back
molecules that interact specifically with antigen-specific immune response molecules via antigenic determinants.
antibodies, B cell receptors (BCRs), T cell receptors (TCRs) or Antigen-presenting cell receptors (ACRs)
Ag-specific immune response molecules
the portions of antigen molecules that physically interact with paratopes of immune response molecules and therefore actually "determine" antigen specificity
antigenic determinants (epitopes)
combining sites
Linear epitopes
continuous and found in polysacchs as well as in both native (nondenatured) and denatured proteins, especially fibrillar proteins
typical size is 5-6 subunits in length
linear epitopes
specificity depends upon primary sequence
linear epitopes
specificity depends upon conformation, or three-dimensional shape, which is a combination of tertiary and quaternary structure ... supported by primary and secondary structure, of course
conformational epitopes
typical size is hard to pinpoint, but sequences of up to 16 amino acids in certain protein antigens have been shown to interact with their complementary paratope
conformational epitopes
discontinuous (involve multiple subunits, often located far apart in the primary sequence of the antigen molecule) and are thus found only in native (globular) proteins
conformational epitopes
have antigenic determinants, but cannot induce immune responses because they lack one or more of the important attributes needed for this function
incomplete antigens
incomplete antigen; artificial monovalent epitope
complete antigens which are able to interact with specific immune response molecules,and can also induce immune responses
determined by foreigness, molecular size, composition and chemical complexity, & processing and presentation susceptibility
Why molecular size is important
larger molecules are more complex and therefor more like to contain foreign epitopes and are also more like to be readily engulfed and processed.
must be processed and presented to trigger T cell responses
protein immunogens
must be reduced greatly by the immune system if immune responses are to occur
Ag Molecule Concentration
generally the most potent immunogens
immunogen potency
proteins first, polysacchs and distant second, nucleic acids generally not immunogenic unless attached to a protein or polysacch.
The more chemically complex an immunogen is...
the more likely it is to have numerous foreign epitopes, and the smaller it can be and still induce an immune response
requires its processing and presentation by APCs
T cell recognition of antigen
Often necessary to prevent tolerance, in which development of an immune response is prevented, sometimes due to the presence of too many immunogen molecules
Removal of excess Antigen
form complexes with fragments of immunogen molecules in responsive animals, but not in non-responsive animals
ACR's and immune responses
controls immune responsiveness by determining the structure of ACRs present on immune cells
genotype & immune response
may cause a lack of responsiveness referred to as tolerance because they "swamp-out" the immune system
high immunogen dosage
generally the best immune response inducers
intermediate doses of immunogen
may not induce immune responses because they:
constitute too few molecules to adequately stimulate enough cells to yield an immune response ... or
induce tolerance
low immunogen dosage
Routes of immunogen administration
Parenteral & Non-parenteral (enteric = ingestion)
parenteral admin: stimulate immune cells in the spleen first
Intravenous (iv) and intraperitoneal (ip) injections
pareteral admin: stimulate immune cells in the lymph node that "drains" the site of injection first
Intradermal (id), subcutaneous (cs) and intramuscular (im) injections
Preferred route for intestinal parasite immunogens & Frequently induces B cell tolerance rather than an immune response
Non-parenteral administration
Function by causing one or more of these effects:
Prolonged persistence of immunogen molecules at the site of injection, Enhancement of co-stimulatory signals, Induction of granuloma formation, Stimulation of lymphocyte proliferation in a non-specific manner
immune response enhancers
Developed the methods leading to the three-dimensional structure of Abs
Poljak ( 1970s, 1980s)
This required a sequence of studies and x-ray crystallography to develop
3-D structure of Abs
Quaternary aggregates of globular protein domains
Antibodies are arranged so that ____ are accesible to antigenic determinants and the ____ can bind to complement and/or ____ receptors on phagocytic cells
a) Fabs
b) Fc
c) Fc
Ab domains are comprised of ...
three dimensionally folded polypeptide structures
These are universal in antibodies and other immuno-relevant structures
This is comprised of the N-terminal domains of Fab
Fv (fragment variable)
The antibody combining sites are loated near the N-terminal regions of the heavy and lght chains that make this up
Fv (fragment variable)
Certain AA's in these sites make up the floor and sides of a shallow groove (or slight projection) on the surface of them that actually interact with antigenic determinants
Fv (fragment variable)
This is responsible for determining the structure, and thus assuring the specificity, of Fv
Immunoglobulin fold
Comprised of ~110 amino acids and are arranged in antiparallel sets of beta-pleated sheets.
Immunoglobulin fold
in the Ig fold, loops that connect the beta-pleated sheets contain amino acids that comprise these
Hypervariable regions (HVRs) or complementarity-determining regions (CDRs) of Abs
Interaction of CDR amino acids with antigenic determinant constituents occurs via
multiple noncovalent interactions
multiple noncovalent interactions include
hydrogen bonding
electrostatic interactions
van der waal's forces
hydrophobic interactions
These determine the specificity and affinity (strength of binding) of Ab combining sites
these are the result of the unique arrangements of AAs that make up Ab combining sites
idiotypic determinants
Biological activities
IgG and IgM complement binding
IgG and IgE FcR binding
IgG transplacental transport
IgA transport through mucous membrane epithelial cells
These are associated with structures in the Fc portion of Ab molecules
Biological activities
Due to mutation-induced changes in a restricted number of AAs, mostly in the constant portions of heavy and light chains
allotypic differences
Genetic basis of Ab combining site diversity
many gene segments or fragments
gene segments are rearranged during B cell maturation
Present in the 5' and 3' ends of each intron, these separate the gene fragments and allow rearrangement to occur in an orderly manner
recognition signal sequences (RSSs)
two types of RSS
heptamer...12(or 23) bp spacer...nonamer
nonamer...12(or 23) bp spacer...heptamer
hybridize with one another, forming the recognition signal for RAG 1 and RAG2
RAG1 and RAG2
Recombination-activation genes; responsible for the actual rearrangement process
the cut out unused intervening sequences of DNA
RAG 1 and RAG2
splice seleted DNA sequences to form AB V region transcriptional units
RAG 1 and RAG2
Ab V region transcriptional units
V-J (light chain)
V-D-J (heavy chain)
These two events activate antibody genes:
generation of a novel V region gene
strengthening the V region promoter
How to generate the novel V region gene
by combination of one of many V region gene segments w/one of several J gene segments or one of several D and one of several J gene segments (heavy)
Strengthens by moving closer to the enhancer found 3' to the J ene segments on the chromosome
the V region promoter