A research standard for human serum immunoglobulins IgG, IgA and IgM.

A pooled human serum, partly diluted, has been distributed into ampoules and freeze-dried in several batches. The freeze-dried material has been examined in an international collaborative assay and certain properties have also been estimated in individual laboratories.On the basis of these tests this material was considered to be suitable for use as a standard for the estimation of IgG, IgA and IgM for clinical purposes using the single-radial-diffusion or similar techniques. Greater uniformity of results than is obtained at present should be achieved if this material were in general use.Estimates of immunoglobulins from different laboratories using this material as a standard showed small but significant variability. This variability was probably related to the heterogeneity of immunoglobulins and of antisera, and it limits the precision of immunoglobulin estimations by techniques at present in use.Batches of this material have been distributed to various centres. 67/68 has been established as the British research standard for human serum immunoglobulins IgG, IgA and IgM for which the unit of potency is defined as the activity present in 0.8147 mg of dry powder. The average activity per ampoule of 67/86 is 100 units of IgG, IgA and IgM. The average activities of other related preparations have been estimated.