Investigation of the Biochemical Relationship between the Blood Group Antigens Xg^a and CD99 (12E7 Antigen) on Red Cells

Abstract

The biochemical relationship between the red cell antigens Xg^a and the MIC2 gene product, CD99 - previously designated the 12E7 antigen - has been examined by immunoblotting and immunoprecipitation analyses of the protein molecules bearing these antigens. Immunoblotting of membrane components and Xg^a-immunoprecipitates with anti-Xg^a has shown that Xg^a antigen is carried on a broad band of apparent molecular weight (M(r)) 24,500-29,500, which consists of a darkly stained component at M(1) 24,500 and a more diffusely stained component at approximately M(r) 26,500-29,500. Immunoblotting of membrane components and 12E7-immunoprecipitates with 12E7, and RFB-l and NaM123 which also recognise CD99, distinguished two bands of M(1) 30,000 and 32,000. A non-radioactive immunoprecipitation technique was employed, which uses chemiluminescence detection of biotin-labelled red cell proteins. The protein of M(1) 32,000, which carries CD99, was identified by this method and the red cell quantitative polymorphism of CD99 was demonstrated. When the Xg^a protein was precipitated from biotin-labelled red cells, a protein of M(r) 32,000 was coprecipitated. This suggests that the proteins carrying the Xg^a antigen and CD99 are associated in the membrane.

Xg Blood Group System

“…It is generally sialidaseresistant [46,50] , but one exceptional CD99 -like antibody did not react with sialidase -treated cells [51] . Sialidase treatment of the cells resulted in a reduction in apparent MW of the CD99 structure [26,27,50,53] . Sialidase treatment of the cells resulted in a reduction in apparent MW of the CD99 structure [26,27,50,53] .…”

“…Immunoblotting of red cells, lymphocytes, various human cell lines, and human -rodent hybrid cells containing a human X or Y chromosome showed that CD99 is associated with a glycoprotein of approximate MW 32 kDa [26,27,50 -53] . Immunoblotting of immunoprecipitates confi rmed that CD99 and Xg a are located on separate structures [26,27] . Immunoblotting of immunoprecipitates confi rmed that CD99 and Xg a are located on separate structures [26,27] .…”

“…Immunoblotting of immunoprecipitates confi rmed that CD99 and Xg a are located on separate structures [26,27] . Petty and Tippett [26] found that alloanti -Xg a co -precipitated Xg a and CD99 glycoproteins, suggesting that these two homologous structures are associated in the membrane, but Fouchet et al . Petty and Tippett [26] found that alloanti -Xg a co -precipitated Xg a and CD99 glycoproteins, suggesting that these two homologous structures are associated in the membrane, but Fouchet et al .…”

XG: the forgotten blood group system

“…Immunoblotting of immunoprecipitates confirmed that CD99 and Xg a antigens are located on different structures, later confirmed to be sialoglycoproteins. 18,19 CD99 and Xg a are associated in the membrane, possibly in the form of a heterodimer. 7,18 The RBC membrane molecule expressing Xg a was first identified in 1989 by Herron and Smith, by immunoblotting and electropheresis.…”

“…18,19 CD99 and Xg a are associated in the membrane, possibly in the form of a heterodimer. 7,18 The RBC membrane molecule expressing Xg a was first identified in 1989 by Herron and Smith, by immunoblotting and electropheresis. 19 Several years later, Petty and Tippett used immunoblotting and immunoprecipitation to show that Xg a is carried on a broad band of apparent molecular weight 24.5 to 29.5 kDa, consisting of a darkly stained component at 24.5 kDa and a more diffusely stained component between 26.5 and 29.5 kDa.…”