Glossary
Purified IgG
Purified IgG is the immunoglobulin fraction separated from serum. Protein A/G purification and peptide-affinity purification are two very different things.
Purified IgG indicates that the immunoglobulin G fraction has been isolated from the remaining components of an antiserum. That term hides a crucial difference, and any datasheet that omits which method was applied is incomplete.
Two unrelated purification methods
Protein A or Protein G purification binds IgG via its Fc region. It strips out albumin, proteases and non-IgG serum proteins and delivers a solution of defined mg/mL concentration that can be conjugated — yet it captures every IgG the animal made, so the fraction specific to your target may still be only a few percent of the total. Protein A and Protein G bind different host species and subclasses with different affinities, which is why the host species is always given.
Antigen-affinity purification runs the serum over immobilised peptide and releases only the antibodies that stick to it. What you obtain is target-specific IgG with clearly lower background, the correct option for immunohistochemistry, conjugation and every quantitative ELISA. The yield is far smaller, and elution at low pH or with chaotropes can harm the highest-avidity clones.
In both cases, purified IgG comes with a concentration in mg/mL, permitting genuine titration instead of the guesswork of dilution factors that whole serum requires.
Related terms and material
polyclonal vs monoclonal · blocking peptide · immunogen. Reference material: antibodies, labeled antibodies. Further reading: antiserum vs purified IgG.