IGG SUBCLASS DETERMINATION IN HUMAN SERA WITH COMMERCIALLY AVAILABLE REAGENTS - COMPARISON OF DIFFERENT ASSAY SYSTEMS

IgG subclass determinations are of increasing importance for the diagn osis of humoral immunodeficiencies. The search for a method which is a ccurate, reliable and suitable for the clinical routine, while utilizi ng commercially available reagents, was the aim of this study. Differe nt assay systems for determination of IgG subclasses were compared. Ra dial immunodiffusion with polyclonal antisera (RID(poly)) proved to be a reliable method for subclass determination in individual human sera . Sera deficient in one or several IgG subclasses as well as several m yeloma proteins were readily and reliably detected. The RID method wit h monoclonal antibodies (RID(mono)) yielded results comparable to thos e obtained with RID(poly) in the IgG1 and IgG2 determination. Differen ces between RID(poly) and RID(mono) were observed, however, in the det ermination of IgG3 and IgG4. These discrepancies were shown to be due to differences in the calibration of the standards as given by the man ufacturers, and not to different recognition of distinct allotypes. Th e results of an enzyme immunoassay (EIA) using commercially available IgG reagents without further purification did not compare satisfactori ly with the results of the RID(poly) method. These discrepancies, howe ver, were assay-inherent rather than monoclonal reagent-inherent.