Human IgG subclass measurements in the clinical laboratory

Abstract

During the past 30 years a vast amount of detailed information has been generated on the physical and biological properties of the IgG-subclass proteins and the subclass distribution of IgG antibodies in immune responses against foreign and self antigens. This is exemplified by two 1986 reviews in Monographs in Allergy (Volumes 19 and 20) that examine basic and clinical aspects of the IgG subclasses and recent developments in our understanding of immunoglobulin subclass deficiencies. It is clear from these and other reports that measurement of the IgG subclass protein and subclass typing of the IgG antibodies is being successfully performed in research laboratories. Availability of excellent, documented monoclonal antibodies to the IgG subclasses will allow these measurements to enter the clinical immunology laboratory. The rationale for measuring each IgG-subclass protein in serum is based on the belief that identification of IgG-subclass deficiencies that often are masked by a normal value for total IgG can be clinically useful. Early identification of selective IgG-sublcass deficiencies can allow explanations and better planning for the patient who has recurrent infections, and possibly more exact treatment with replacement therapy. Clinical importance of the subclass typing of IgG antibodies with defined antigenic specificity is based on a belief that the identification of different subclass patterns can prove useful in determining the ultimate protective or destructive effect these antibodies will elicit once they are bound to ciruculating or tissue-bound antigen. IgG-subclass measurements represent an important frontier in clinical immunology laboratory testing.