A Second Example of —/— or Rh_null Blood

Abstract

The second example of a —/— or Rh null , LW‐negative individual is described, who delivered a mildly affected infant and produced only anti‐e. The proposita is a member of a large family and their probable genotypes are known. The parents, who are not related to each other, are R 1 R 1 , father, and R 1r mother, so that the proposita could be either [ R 1 R 1 ) or [ R 1r ], but none of the Rh antigens are expressed. Her husband is rr and their first infant is R 1r . Thus the proposita transmits R 1 to her child. Scoring titrations reveal that 12 out of the 16 members of the family, including the parents of the proposita and her child have diminished reactivity of D, C, c, and e. All members of the family except the proposita are LW‐positive. Theoretical aspects are discussed in terms of an independent amorph X 0r which when present in double dose prevents expression of Rh and LW genes. The (our normal individuals are represented as X 1r X 1r which act on precursor substance to produce full expression of Rh and LW genes. In the 12 heterozygotes, X 1r X 0r , Rh antigens are weaker but not LW.