The quantification of human IgG subclasses in reference preparations

Three laboratories took part in an investigation about the possibilities of quantitative determination of IgG subclasses. Polyclonal monospecific antisera were used in combination with different kinds of calibrators to assess the IgG subclass levels in three W.H.O. reference preparations. IgG 1 could be determined with satisfactory precision; for the other subclasses the quantification was less precise. The precision was dependent on the antisera for IgG 1, IgG 2 and IgG 4 but mainly on the calibrators for IgG 3. Mass units are to be preferred to relative units. W.H.O. reference preparation 67/97 is proposed as a reference for determination of IgG subclasses in mass units. The target values are 5.0 g/l for IgG 1, 2.6 g/l for IgG 2, 0.4 g/l for IgG 3 and 0.5 g/l for IgG 4. These values add up to a total IgG value close to earlier W.H.O. estimates.