The b(51)Cr red cell survival studies showed the spleen to be the preferential site of red cell destruction, and splenectomy produced a dramatic improvement in red cell survival. Nash and Shojania (1987) restudied the woman reported by Chown et al. Rh antigens constitute part of the red cell membrane. When homozygous, both the suppressor gene and the Rh amorphic gene (Rh-null) result in anemia, shortened red cell survival, increased fragility, stomatocytes, and increased fetal hemoglobin. The authors compared this 'modified' phenotype (Rh-mod) with the Rh-null phenotypes that had been described. The modifier was clearly not linked with the Rh locus. A homozygote also had a weak reaction with anti-U and anti-S, compensated hemolytic anemia, and unconjugated hyperbilirubinemia. Heterozygotes showed weakening of reaction of all Rh antigens. ![]() (1972) described the effects of a genetic modifier for the Rh blood groups. Clinically, Rh-deficient individuals exhibit a mild to moderate chronic hemolytic anemia accompanied by a varying degree of spherostomatocytosis (summary by Huang et al., 1999).Ĭhown et al. Whereas Rh-null cells lack all Rh antigens, Rh-mod cells display a markedly reduced antigen expression. The RH-null regulator phenotype thus arises from inactivating mutations in RHAG on a D-negative background (summary by Huang et al., 2000). The absence of the D antigen, produced by the RHD gene, is common in the human population the D-negative phenotype may result from deletion or genetic alteration of the RHD gene. Four genes must therefore be silenced to produce the RH-null phenotype. The RH locus contains the RHD ( 111680) and RHCE genes tandemly arranged at chromosome 1p36-p34. ![]() ![]() The amorph type arises from mutations at the RH locus itself that silence Rh expression. The regulator type is caused by mutation in the RHAG gene ( 180297), which encodes the Rh50 glycoprotein that is crucial for the surface disposition of Rh antigens. Two RH-null types, the regulator type (RHNR) and the amorph type (RHNA 617970), arising from independent genetic mechanisms have been distinguished. The RH-null phenotype designates rare individuals whose red blood cells lack all Rh antigens.
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