Standardization of IgG subclass antiserums for use with sensitized red cells

The only IgG subclass antiserums standardized for use with red cells are those sold by the Netherlands Red Cross. Their recommended method is a sedimentation antiglobulin test (AGT) not generally used in the USA. Some years ago we tested the antiserums for sensitivity and specificity using the routine centrifugation AGT and found the methods comparable. More recently, we have become concerned since the antiserums are being used by a variety of methods other than the recommended procedure. It is well-known that it is difficult to prepare subclass antiserums without contaminating antibodies to other IgG markers. Thus, we thought it worthwhile to standardize the antiserums with particular emphasis on specificity using several different technics. We found that some methods that have been used to define the subclass of red cell-bound IgG were inappropriate, and led to many false positive results.