-blood

-first responder

-first to be expressed because don't need class switching

-have relatively low affinity

-membrane bound

-unknown function

-blood, intercellular

-4 subclasses

-high affinity/avidity antigen binding site

-good viral/toxin/bacterial neutralizer

-good opsonizer

-activates complement system

-bound to mast cells

-lowest level in blood

-if encounter complementary antigen, mast cell gets triggered to release histamines

-control parasites

-epithelial and mucosal surfaces, blood

-principle Ig in secretions

-dimer on mucosal surfaces

-monomer in tissue, lymph nodes and blood

-less effective at opsonization than IgG

-good neutralizer

-make serial dilution of test serum

-add constant amount of virus to each well

-add constant amount of red blood cells to each well

-incubate

-read results

-endpoint titer is reciprocal of last serum dilution which prevents agglutination