1-Antibodies Flashcards
features of adaptive immunity
- specificity
- immunologic memory
- diversity
- self regulation
- discrimination
specificity
adaptive immune response generated towards determinants/epitopes
bc lymphocytes have cell membrane receptors for one specificity
immunologic memory
memory cells make faster and more vigorous resp upon re-exposure to antigen
memory cells more sensitive to stim by antigen than antigen-naive lymphocyte
diversity
pre-existing antigen specific lymphocyte react with 1x10^9 (a ton) of antigens
expression of cell surface receptors that can react with diverse number of antigens
self regulation
regulation via
1. removal of antigen so no immunologic stimulation
2. activated lymphocytes die w/i short period by apoptosis
3. regulatory immune mechanism
discrimination of self vs non
adaptive immune resp directed normally vs foreign antigens NOT self antigens
immune cells that are specific for self are destroyed/regulated
lead to autoimmune disease occur if lost
immunogenicity
properties of an antigen that promote an immune response
big immune resp = high immunogenicity
ex. bacteria/fungi high bc so foreign
adjuvant
immunogenicity is inc
prolonged retention of an antigen so time for more vigorous immune resp can occur
ex. alum, mineral oil, lipids
antigenicity
properties that allow a substance to react with an antibody
haptens
small molecules that cannot induce antibody formation BUT can react with antibody that is specific for it aka hapten = antigen NOT immunogen
-must be coupled to a carrier molecule to induce antibodies
features of immunogens
- size - bigger size = better immunogen
- internal complexity- more complex = more immunogenic, proteins good
- degradability- immunogen processing must occur, proteins > peptides
- foreigness- tolerance to self antigens so must be foreign
- accessibility- easy to reach areas more likely induce immune response aka immunodominant areas
antigen conformation
types of determinants
conformational determinants- amino acid residues must be in 3D structure to bind antibody, if denatured not work
linear determinants- adjacent aminos will bind antibody when denatured, not accessible if native strucutre
neoantigens- new antigens formed by proteolysis to make new determinant
T lymphs only recog linear determinants
types of antigens
most common are proteins and most immunogenic
-from serum proteins or microbes
also lipoproteins (cell membranes), polysaccs (bacterial capsules), glycoprotein (blood), polypeps (hormones), nucleic acids (cells, microbes)
antibodies/immunoglobulins
general
-present in body humors/fluids
-effects mediated by glycoproteins binding to antigen specifically
-will not be present until stimulated/exposed by antigen
‘gamma globulin’ also used
antibody locations
-surface of B lymphocytes antigen receptors specific to one, if naive-B then have both IgM and IgD
-blood plasma and tissue fluids
-surface of mast cells/basophils IgE
-secretory fluids (mucus and milk)
antiserum
antibody containing serum
-fluid portion of blood after cellular parts clotted
either polyclonal (pop of antis that bind 1+ antigens) OR monoclonal (antibody bind only 1)
antibody titer
reciprocal of the LAST dilution of antiserum that still yields a demonstrable antibody binding reaction
aka take the last reaction and inverse it
antibody strucutre
2 heavy chains + 2 light chains
heavy are connected to each other and to light chains by disulfide bonds
constant and variable regions
-variable is what forms antigen bind site
subdivisions of variable region
- hypervariable- binding surface, varying amino acids here make antigen specificity
- framework- support hypervariable
antibody properties
structural, isotypes
-IgA/D/G have hinge region for flexibility
-two isotypes= secretion or membrane form, D has membrane only
-secretory form of M and A have j chains for pentamer/dimer/trimer formation
-isotype switching allow single antigen specificity for diff functions
M is pentamer, A dimer or trimer
proteolysis of antibodies
either produce two Fab fragments each w/ binding site + 1 Fc frag (split in 3) Papain OR
single Fab with 2 binding sites + no surviving Fc frag (split once + itty bitty frags) Pepsin
antibody classification
based on diffs in amino seq of heavy chains
IgA/D/E/G/M
IgG has subisotypes 1-4
IgA has 1-2
antibody monomers
IgG
IgE
IgD
polymer antibodies
IgM
IgA
IgG
-most abundant immunoglobulin in normal serum
-secretory form is monomer
-activates complement classical pathway
-IgG1 and 3 can opsonize
-coat tumor cells or virus infected for ADCC
-cross placenta for immunity to fetus
-in mother’s milk so taken up by infant gut lumen and transported into blood
IgM
-secretory form is pentamer
-excellent complement activator better than G
-predominate antibody in primary immune resp
IgA
-mediator of mucosal immunity
-@ tears, saliva, colostrum, milk
-monomeric in serum, dimer in secretory held by j chain
-eosinophil mediated ADCC of parasitic infections
mucosal immunity mechanism
IgA gets transported thru mucosal cells by coupled to secretory piece to protect it from proteolytic enzymes and glue it to mucus
secretory piece from epithelial cell Fc receptor
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
IgD
-very low in serum but primarily @ surface of antigen naive B lymphs with IgM
-important for transduction of signals across plasma membrane for antigen driven B cell activation
affinity
definition
strength of binding for antigen of 1 antigen combining site
for a pop of antibodies affinity will inc with repeated immunization with an antigen
avidity
overall strength of attachment based on how many combining sites the antibody has bound
allotype
differences in constant regions of antibodies but same isotype bc of multiple alleles
idiotype
collection of hypervariable regions by heavy and light chains that form antigen binding site
