An Lu(a-b-) phenotype caused by an X-linked recessive gene

The family of a male Lu(a-b-) propositus whose red cells showed some characteristics of the dominant and some of the recessive type of Lu(a-b-) phenotype was studied. The investigation revealed a third genetic background for this rare phenotype, an X-borne suppressor recessive in effect. The notation proposed is XS1 for the normal gene and XS2 for the suppressor gene which affects the expression of Lutheran and other antigens.