The absolute quantification of human IgM and IgG: standardization and normal values.

Nephelometric, turbidimetric and radial immunodiffusion methods are described, which permit valid, reproducible determination of human IgM and IgG by weight. Subgroups of IgM, 7S-IgM and subclasses of IgG did not interfere with these methods. For IgG the International Unit represented a constant weight quantity in agreement with official WHO estimations. For IgM the IU was not constant and much lower values are found. It is therefore suggested that the IU should be abolished for human IgM and IgG. Absolute values for IgM levels are presented for both sexes and for age groups in the range of 5-80 years. The figures showed significant variation with sex and age.