The following Table compares the relative affinity of Protein A and Protein G for human immunoglobulins (antibodies).
| Immunoglobulin type and class | Protein A | Protein G |
| lgG1 | +++ | +++ |
| IgG2 | +++ | +++ |
| IgG3 | – | +++ |
| IgG4 | +++ | +++ |
| IgA | + | – |
| IgD | – | – |
| IgE | +/– | – |
| IgM | + | – |
| – : No binding +/– : no or weak binding + : weak binding +++ : strong binding | ||
