Changes

*There are various methods to separate the antigen-antibody complexes from the free antigen:

*There are various methods to separate the antigen-antibody complexes from the free antigen:

**Precipitate complexes using secondary isotype-specific anti-immunoglobulin

**Precipitate complexes using secondary isotype-specific anti-immunoglobulin

**If complex contains IgG, it can be removed by mixing with formalin-killed ''Staphylococcus aureus''- protein A of ''S. aureus'' has a high affinity for IgG

**If complex contains [[IgG]], it can be removed by mixing with formalin-killed ''Staphylococcus aureus''- protein A of ''S. aureus'' has a high affinity for [[IgG]]

*** Removal of the complex by either of these methods leaves an amount of free labeled antigen in the supernatant (liquid section from precipitation)- the radioactivity of this can be measured and the value taken away from the total amount of labeled antigen added (known amount)= amount of bound labeled antigen

*** Removal of the complex by either of these methods leaves an amount of free labeled antigen in the supernatant (liquid section from precipitation)- the radioactivity of this can be measured and the value taken away from the total amount of labeled antigen added (known amount)= amount of bound labeled antigen

**A number of solid-phase RIAs have been developed

**A number of solid-phase RIAs have been developed