Abstract
1) Fractionation of human sera with DEAE ion-exchange cellulose column gave three fractions: the first containing most of the IgG, the second in which IgA is eluted, and the third with IgM. Sera were selected from about 300 mothers, which possessed anti-A or anti-B antibodies with similar titers in the three fractions, IgG, IgA and IgM.
2) Agglutination tests using various methods revealed that IgG antibodies showed the peculiarities of the incomplete antibody, while IgA and IgM were complete agglutinins.
3) The thermal optimum was tested for IgG, IgA and IgM antibodies, but no significant difference was observed in the range from 4°C to 37°C.
4) Treatments which are usually used for the detection of so-called immune anti-A or B were applied to each fraction. Soluble blood group substances readily neutralized IgA and IgM, but only reduced IgG antibody activities. By the heating test, IgM was most sensitive, IgG was unexpectedly weak, and IgA was most resistent. Mercaptoethanol-treatment left IgG unaffected, moderately weakened IgA, and completely deprived IgM of the activity.
5) Presence of hemolytic activity in each fraction differred from case to case and was not well related to the agglutinating activity.
