A routine method for assaying the anti-toxoplasma IgM antibodies. Latex agglutination test on human sera preabsorbed with protein A-bearing staphylococcal cells.

The authors investigated the procedure which demonstrates, by means of the latex agglutination test (LA) the residual IgM antibody activities in sera preabsorbed with protein A-bearing Staphylococcus aureus and evaluated the usefulness of this technique with the following results. (1) LA (Toxotest-LA, Eikenkagaku Co.) gave clear-cut and reproducible agglutination patterns. Its specificity was comparable to that of HA and its sensitivity was somewhat lower than that of HA. (2) The absorption of 0.2 ml of 1:10 dilution of many test sera with the sediment of 0.5 ml of a 10% bacterial suspension for ten minutes or more provides the suitable condition for the absorption procedure. (3) HA-positive 183 sera revealed no residual antibody activities after absorption. These are supposed to derive from persons with a long-standing infection. Sera from 4 laboratory infection cases, from 2 toxoplasmic lymphadenopathy cases and from a pregnant woman, showed more or less residual activities. In 5 out of 7 sera tested, the residual activities were 2-ME sensitive, indicating the presence of specific IgM antibodies. (4) The specific and the total IgM were reduced slightly by the absorption procedure.