Antigens and Antibodies Flashcards
5 features of adaptive immune response
Specificity Immunologic Memory Diversity Self-Regulation Discrimination of Self vs. Non-self
Specificity
due to lymphocytes having cell membrane receptors
each lymphocyte has just one specificity
Immune responses are generated toward determinants/epitopes
Immunologic Memory
Faster and more vigorous immune response upon re-exposure to antigen
Memory cells
more sensitive to stimulation by antigen than antigen-naive lymphocytes
Diversity
you can make a lot of different lymphocytes against lots of things
this is due to the expression of cell surface receptos that can react with a diverse number of antigens
immune responses abate with time because of:
removal of antigen
activated lymphocytes dying within a short peroid of time by apoptosis
regulatory immune mechanisms
Discrimination of self vs. non-self
immune cells specific for self are usually destroyed or regulated
adaptive immune responses are normally directed against foreign antigens
autoimmune disease occurs when discrimination is lost
Immunogenicity
properties that promote an immune response
Antigenicity
properties that allow a substance to react with an antibody, used loosely to describe an immunogen
Haptens
small molecules that cannot induce antibody formation but can react with antibody that it is specific for.
Must be coupled to a carrier molecule to induce antibodies
Is an antigen, but not an immunogen
5 most important features required in order to generate an immune response against an immunogen
Size (larger the better)
Internal complexity (more complex the better)
Degradability (immunogen processing must occur)
Foreignness (has to be foreign)
accessibility (easy to reach areas more likely to induce an immune response)
Linear determinants
formed by adjacent amino acids. T lymphocytes can only recognize these.
conformational determinants/epitopes
amino acid residues from different parts of the protein brought together in 3D space
neoantigens
new antigens formed by proteolysis, phosphorylation
Most common, most immunogenic type of antigen to which the human immune system is most frequently exposed
Protein antigen
Characteristics of antibodies
glycoprotiens that mediate their biological effects by binding to antigen in a very specific manner
not present until stimulated by antigen
Locations of antibodies
surface of B lymphocytes
blood plasma and tissue fluids
surface of mast cells/basophils
secretory fluids (mucus and breast milk)
Monoclonal antiserum
antibodies that bind one specific antigen
Polyclonal antiserum
population of antibodies that collectively can bind to more than one particular antigen
Titer
reciprocal of the last dilution of antiserum that still yields a demonstrable antibody binding reaction. To get the number, take the inverse of the smallest dilution where you get a reaction
heavy chain
connected together by covalent disulfide bonds
light chain
connected to heavy chains by disulfide bonds, form the antigen binding site
hypervariable regions
fingertips
form the binding surface
framework regions
fingers
support the hypervariable regions
hinge region
allows for flexibility of antibody arms
5 antibody classes
IgG, IgM, IgA, IgD, IgE
IgG
most abundant immunogloblin in normal serum
secretory form = monomer
activates complement by the classical pathway
crosses placenta to convey protective immunity to fetus, in mother’s milk
main antibody produced in secondary immune response
IgA
mediator of mucosal immunity
present in tears, saliva, colostrum, and milk
monomeric in serum, dimer in secretions
dimer held together by J-chain
eosinophil-mediated ADCC of parasitic infections such a helmiths
IgM
secretory form = pentamer
excellent activator of complement (even better than IgG)
predominant antibody produced in primary immune response
IgE
secreted as monomer
eosinophil-mediated ADCC of certain parasites
binds to cell surface receptors for IgE on basophils and mast cells to mediate allergies and anaphylaxis
Receptor is high affinity
IgD
very low concentrations in serum
primarily on the surface of antigen-naive B lymphocytes
important in the transduction of signals across the plasma membrane to result in antigen-driven B cell activation
Affinity
strength of binding for antigen of one antigen combining site. IgG has greater affinity than IgM
Affinity maturation
average affinity for a population of antibodies will increase with repeated immunization with an antigen
Avidity
overall strength of attachment which takes into account how many antigen combing sites the antibody has bound. IgM has greater avidity than IgG
Allotype
differences in the constant regions of antibodies (of the same isotype) between individuals due to the presence of multiple alleles of the constant region genes in the human population
Idiotype
collection of hypervariable regions contributed by heavy and light chains that form the antigen binding site