H-deficient blood groups of Reunion island. II. Differences between Indians (Bombay Phenotype) and whites (Reunion phenotype).

Two variants of recessive, H-deficient nonsecretor individuals (h/h, se/se) were identified on Reunion Island: (1) H-negative individuals corresponding to the classical Bombay phenotypes (OhO, OhA, OhB, OhAB) who lack completely the H antigen on their red cells; all of them were Indian and had strong anti-H antibodies reacting with normal O and Oh red cells from whites; and (2) H-weak individuals (Oh, Ah, Bh, ABh). This phenotype represented the majority (85%) of the H-deficient phenotypes on Reunion Island, and all of them were white. They had only a weak expression of the H antigen and showed small but detectable amounts of ABH antigens on their red cells. Their anti-H antibodies reacted with normal O erythrocytes, but failed to react with Oh red cells, regardless of the ethnic origin of the donor. They were all from the same geographical area on the Island (Cilaos) and showed homogeneous titers of anti-H antibodies in sera. We propose to call this particular variant of weak H phenotype, belonging to the so-called para-Bombay series, Reunion.