Published online by Cambridge University Press: 01 August 2014
The levels of ABO plasma agglutinins were studied in 47 MZ and 30 same-sex DZ pairs of twins having the same blood group. The degree of genetic determination of this characteristic, as ascertained by the comparison of average titers and titration scores, does not seem to be high; despite the fact that the correlation coefficients were always lower among DZ, the F ratio was significant in relation to the anti-B of A persons only. The presence of these antibodies was also investigated in the saliva of 30 MZ and 26 DZ pairs. Since about the same degree of discordance was observed among these two types of twins, the role of inheritance in the variability of this trait must be low.