A weak B antigen with serologic reactivity between B₁ and B₂ red blood cells found in a Chinese family

During a serologic study on red cell samples from individuals representing three generations of a Chinese family, an unusual pattern of reactivity was noted in a sample from a daughter of an A₁B₂ individual. The results of direct ABO grouping, titration, and adsorption studies demonstrated that the red blood cells (RBCs) from the proposita and two of the proposita’s uncles (1) expressed more B antigen than group B₂ RBCs but less than group B₁ RBCs; (2) expressed the B₁ antigen but at a lower level than group B₁ RBCs; and (3) expressed more H antigen than B₁ RBCs but slightly less than B₂ RBCs. The saliva from the proposita contained soluble B and H antigens, and her serum contained a weak B-gene-specified transferase. Serologic reactivity of her RBCs was intermediate between that of B₁ and B₂ RBCs. That is similar to reactivity of A_int RBCs, which is intermediate between A₁ and A₂ RBCs. The proposita may represent a B_int phenotype. Immunohematology 1993;9:11.