A family is presented in which the propositus and 2 siblings, apparently in group O, have in their sera anti-H in addition to anti-A and anti-B. Inspection of the family tree reveals apparent violations of Mendelian heredity which can be explained on the basis of a rare suppressor gene which in the homozygote state suppresses in the propositus the actions of gene B and secretion gene Se. The genes B and Se are fully expressed when transmitted to her offspring who are heterozygous for the suppression gene. The same mechanism may be assumed to operate in the 9 other so-called group O bloods containing anti-H.

The antibody in four cases of P.C.H. sera was shown to correspond in specificity to anti-P + PI (anti-Tja). The specificity was revealed by coldwarm lysis and in one case tested by direct agglutination in the cold.

The second example of a —/— or Rhnull, 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 R1R1, father, and R1r mother, so that the proposita could be either [R1R1) or [R1r], but none of the Rh antigens are expressed. Her husband is rr and their first infant is R1r. Thus the proposita transmits R1 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 X0r which when present in double dose prevents expression of Rh and LW genes. The (our normal individuals are represented as X1rX1r which act on precursor substance to produce full expression of Rh and LW genes. In the 12 heterozygotes, X1rX0r, Rh antigens are weaker but not LW.

No abstract