[Hemagglutination inhibition test for rubella virus: control of the removal of complete non-specific inhibitors].

A method showing whether the inhibitory activity of a serum, with a low rubella HAI titer, is due to specific antibodies, or to the incomplete removal of non-specific beta-lipoprotein inhibitors, is described. Serum absorption with Staphylococcus aureus removes over 95% of the IgG, and a smaller amount of the other Ig, beta-lipoproteins and albumin, whereas Staphylococcus epidermidis absorbs about 20% of all Ig, beta-lipoproteins and albumin. This means that a serum with anti-rubella IgG displays the same, or at most a slightly depressed HAI titer after absorption with S. epidermidis, whereas S. aureus leads to at least a 16 fold reduction. By contrast, a serum with no antibodies, in which inhibition is due to non-specific inhibitors, will show an equally reduced HAI titer after absorption with each strain.