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Further investigation of the pellicle formed in 2 h on cleaned human teeth in vivo is reported. Electron micrographs demonstrating the presence of a thin organic layer 2 h after the teeth were brushed with pumice are shown. The pellicle material contained several sugars, with glucose as the most abundant. Material from secretors and non-secretors of blood group substances was analysed, but no difference in carbohydrate composition was found. Tests for biological activities indicated the presence of blood group substance and virus haemagglutination inhibition activities in the 2-hour pellicle.

A significant fraction (30%) of the genetically determined variance in plasma concentration of the von Willebrand factor antigen (vWf:Ag) has been shown to be related to ABH determinants. Individuals with blood group O, who have the highest amounts of blood group H substance, have the lowest concentration of vWf:Ag. The Lewis substances, Le(a) and Le(b), are biochemically closely related to the ABH substances as both can be produced from the same precursor substance. We studied the effect of the presence of the Lewis antigens on the plasma concentration of vWf:Ag and factor VIII antigen (VIII:Ag) in 323 individuals of different ABO groups from a series of twins and in 58 blood donors of blood group O. Among persons belonging to blood group O, those with the Le(a) antigen had a higher concentration of both vWf:Ag and VIII:Ag than individuals lacking Le(a). Le(a+b-) people are nonsecretors and Le(a-b+) people are secretors of ABH substance. Thus, the lowest concentration of vWf:Ag and VIII:Ag was found in group O secretors. The effect is most likely due to an effect of the secretor locus. This finding may be of importance for the detection of carriers of hemophilia A and for the diagnosis of type I von Willebrand disease.

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The frequency of irregular blood group antibodies detected for the first time in pregnant women during the period 1975-80 has been examined. Whereas Rh(D)-negative gravidae in Norway are examined immuno-hematologically three times during pregnancy, Rh(D)-positive women are tested once only, usually early in pregnancy. Nevertheless, about one-third of the new cases of immunization within the Rh system were found in the Rh-positive women. In the latter, anti-E and anti-c were the Rh antibodies most frequently encountered. Among other irregular antibodies which can cause hemolytic disease of the newborn (HDN), those of the Kell and Duffy systems are the ones second in frequency and clinical significance to the Rh antibodies. In the present series about 40% of the new cases of immunization within the Rh, Kell and Duffy systems were found in Rh-positive women. This proportion would undoubtedly have been greater if also the Rh-positive women had been retested for the presence of irregular blood group antibodies towards the end of the gestation. Such a retesting of Rh-positive gravidae is desirable both for a better prediction and early diagnosis of HDN and to facilitate the procurement of compatible blood if the woman should need an emergency blood transfusion.