The NA"null" phenotype of a young man is caused by an FcγRIIIB gene deficiency while the products of the neighboring FcγRIIA and FcγRIIIA genes are present

Abstract

 A 27-year-old man with an allergy to house dust mites was found to lack the FcγRIIIb on his neutrophils. Cell surface marker and PCR techniques were used to investigate possible reasons for this deficiency. Agglutination and immunofluorescence assays using the man's neutrophils together with NA1- and NA2-specific antibodies were negative, and there was no reaction with the FcγRIII-specific mAb 3G8. Indirect immunofluorescence demonstrated the presence of the CD24 molecule, which, like the FcγRIIIb, is anchored to the cell membrane by glycosylphosphatidylinositol. Thus a lack of the FcγRIIIb cell membrane anchor was excluded. PCR analysis confirmed the absence of the NA1 and NA2 alleles. The individual was therefore typed as NA"null". The products of those genes located together with the FcγRIIIB gene within a complex on chromosome 1 (q23–24) were examined. FcγRII was demonstrated on monocytes and B cells with the use of FcγRII-specific monoclonal antibodies. About 5% of the individual's peripheral blood monocytes were positive with the 3G8 antibody, indicating the presence of FcγRIIIa. From these data we concluded that the FcγRIIIb deficiency on the neutrophil cell surface of this individual is due to a lack of the FcγRIIIB gene while excluding a lack of the FcγRIIA and the FcγRIIIA genes.