Serum IgG subclass levels are reported on 70 patients with known primary immunodeficiency syndromes. Analysis of the data on the 28 patients with common variable immunodeficiency suggest that the deficit in subclasses is not generally proportionate. Some subclasses appear to be more strongly affected than others. The pattern suggests a hierarchical involvement with the order: IgG4 greater than IgG2 greater than IgG1 greater than IgG3. There appears to be a closer relationship between IgG1 and IgG3 levels than between IgG2 and IgG3 or IgG1 and IgG2 levels. The data are consistent with the hypothesis that there is a sequential increasing impediment of the programmed cascade for downstream heavy chain constant region gene rearrangements.
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