humoral response Flashcards
how is humoral immunity
humoral immunity: immunity that does not require the presence of cells (blood soluble)
what part of antibodies recognises antigens
CDR looops at end of antigen
what section of antibody fragment is the same in all antibodies
Fc fragment does not undergo recombination events (VDJ recombination), same in all antibodies
what is functions of B cells
when antibody is attached to cell its only function is recognition of antigens
when B cells start to secrete antibodies it is a plasma cell, only function is secretion of antibodies
what are different forms of antibodies (not IgA etc)
antibody can be both a transmembrane protein and a globular protein by being able to transcribe specific transmembrane region exons, allowing it to have a transmembrane region, it can also not transcribe these exons to aloow secreted version
what is serum immunoglobulin
serum immunoglobulin: antibodies found in serum, second most concentrated protein in blood after albumin, all left over antibodies from immune responses
how do immune responses compare in speed of action
secondary response is much faster and stronger than primary immune response
what are different types of antibody, where aer they found
IgG is most common isotype in blood, serum immunoglobulin is IgG
IgA is found in secretions not in blood (including breast milk)
IgD and IgM found on the surface of nieve b cells since their exons appear first in exon sequence for constant region
also IgE
these types differ in terms of which type of heavy chain they have
(see biochem notes)
what antibodies form multimers, how are these beneficial
IgA forms dimers, IgM forms pentamers, both polymers are joined together by something called a J chain
IgM pentamers contain 10 binding sites, pentamers circulate regularly, dimers are secreted
surface of bacteria contains repeated sequences, is a polyvalent antigen (antigen has multiple binding sites)
IgM polymers can bind repeatedly to same bacterium
the avidity, the combined affinity of one molecule to bind to multiple binding sites, the avidity of pentavalent binding is a hundred thousand more than a single binding site
because IgM polymers have higher avidity the body produces lots of this to increase affinity of antibodies
what is a negative of antibody polymers
the problem with making IgM all the time to create lots of high affinity antibodies is that immune complex formation can occur, where antigen-antibody networks form on large scale by forming large chains which become insoluble and can cause unwanted inflammation
what types of antibody are involved in what stages of response
early on in response lots of IgM is made since you cannot make high affinity IgG, later responses use high affinity IgG
effector functions of antibodies: neutralisation of toxins and viruses (IgG), direct opsonisation and phagocytosis (IgG), complement (IgM)
how do antibodies neutralise toxins, give an example of this , how do they neutralise viruses and bacteria
neutralisation: if toxin binds to receptor it causes pathology, however if it binds to antibody it cant bind to receptor and the complex can be disposed of (antibody acts like a competitive antagonist), example is tetanus toxin
tetanus toxin immunity is humoral
if virus binds receptor it can enter cell and cause disease, antibody binding prevents this
neutralisation works well with toxins and viruses however bacteria are too large to be blocked in this fashion and can live extracellularly
how do antibodies bind to phagocytes
Fc receptors are on Fc fragment and allow phagocytes to bind to antibody
binding of FcRgamma (IgG binding) not only facilitates uptake but activates phagocytic killing mechanisms
bound antibodies allow bacteria to be identified more easily (part of opsonisation)
pathways leading to complement activation involve antibodies (classical pathway is triggered by antibody bound to microbe)
how are monoclonal antibodies produced
monoclonal antibodies: mouse is immunised with target protein, the B cells that are produced are then immortalised, the b cells are then screen to get the correct cell, that cell with then secrete desired antibodies.
(see biochem)
