Crossreacting Antibody and Saliva Agglutinins

183 samples of saliva were collected from women 2–6 days post-partum and examined for the presence of anti-A and/or anti-B antibodies. The presence or absence of such antibodies was correlated to the presence or absence of maternal immune antibodies and cord antibodies of anti-A and/or anti-B specificity. In 27 group A mothers there were four with saliva anti-B three of whom belonged to subgroup A₂. Two group A mothers had children of group O who had anti-A in the cord serum. In 11 group B mothers there were three with anti-A agglutinins in their saliva. In 145 group O mothers there were 75 with saliva anti-A, anti-B, or anti-A + anti-B agglutinins. In the majority of cases, but not in all the saliva antibodies were destroyed by mercapto-ethanol. The incidence of saliva antibodies varies with the blood groups, increasing from A₁ to B to A₂ to O. The significance of these findings is discussed. In group O persons there was a statistically significant association between the presence of saliva antibodies of the ABO system and

• (a) the presence of immune anti-A + anti-B in the corresponding maternal sera;
• (b) cross-reacting eluates obtained from A cells after contact with corresponding maternal sera;
• (c) agglutination of A_x cells by corresponding maternal sera;
• (d) and – in group O children – the presence of anti-A and/or anti-B antibodies in the corresponding cord sera.

In the majority of cases the presence of saliva antibodies is closely associated with all four of these serological features; there are, however, instances when there is only association with one or two of them, in agreement with Landsteiner's statement, that antibodies formed in response to one determinant group are not absolutely identical but vary around a main pattern.