Serologic markers and chromosome variants in a pair of chimeric twins.

A pair of chimeric twins, T.S. (male) and M.R. (female) first examined in 1970 are reinvestigated in order to determine if the proportions of admixture of red cells in their blood are unchanged, and if erythrocytes and leukocytes show the same percentage of admixture. T.S., M.R. and their family are investigated for HLA, serum types, and erythrocyte antigens and enzymes. A quantitative determination of 'foreign' cell populations in the blood of each twin is attempted for the systems ABO, and HLA, and for sex chromosomes in PHA stimulated lymphocytes. The results for the ABO system obtained by agglutination technique and by a double-layer immunofluorescence technique indicate that the population of M.R. erythrocytes in T.S. has decreased during the 7-year period, and is now below half the size found in 1970. Erythrocytes and leukocytes show the same percentage of admixture in both twins.