AN ISRAELI FAMILY WITH 6 CISAB MEMBERS - SEROLOGIC AND ENZYMATIC STUDIES

BACKGROUND: The cisAB blood type is a rare phenomenon in which both th e A and B blood types are inherited from a single parent. Several form s of this phenotype have been characterized that differ with respect t o serologic reactions and the activities of the gene-encoded blood gro up A and B transferases. STUDY DESIGN AND METHODS: The cisAB blood typ e was suspected when a baby typed as blood group O was born to a mothe r whose blood group was AB, Family studies revealed four generations i n whom the pattern of inheritance could be explained only by the inher itance of the cisAB genotype. Blood and saliva samples from the family were tested serologically and assayed for the relevant glycosyltransf erases. Samples suitable for DNA analysis were not available. RESULTS: Six family members were shown serologically to be of the cisAB type. The A and B transferases in the sera of these individuals were 20 to 3 5 and 25 to 50 percent of those obtained for A and B individuals, resp ectively. The enzymic characteristics of the A and B transferases were determined. The A transferase in the sera of the cisAB persons did no t bind to agarose beads. CONCLUSION: The family described carries the cisAB gene, which encodes production of A and B transferases that diff er from those of ''normal'' A, AB, and B controls. This variant has pr operties that are distinctly different from those described in other r eports.