NDV-O agglutinins and heteroagglutinins in sera of blood donors.

In sera of healthy blood donors advancing age was accompanied by a decrease in the levels of agglutinins against human group O erythrocytes modified by Newcastle disease virus (NDV-O agglutinins) and of heteroagglutinins against sheep, guinea-pig and rabbit erythrocytes. Significant correlations of titres existed between the different heteroagglutinins, but not between these and the NDV-O agglutinins. The origins and interrelations of the natural agglutinins are discussed.