RESUMO
The described ELISA method was developed for the examination of antitoxoplasmatic IgM. It is a double, i.e. 4-layer sandwich with the following layers: 1. anti. IgM antibody, 2. the examined serum in a uniform dilution of 1:100, 3. antigen + antitoxoplasmatic conjugate, 4. combined in a mixture prepared in advance. Thus the reaction is shorter but also more sensitive. The components in all three steps are combined for one hour at 37 degrees C. The entire process takes four hours. With regard to the course of the final answer in this type of ELISA reaction it is better to express the results by the level of the attained plateau of optic density than by a titre. The sera are thus examined in a uniform dilution of 1:100 and the results are expressed by a coefficient, the ratio of optic density of the examined serum to the optic density of the pooled negative control serum. By this evaluation the deviation of the mean is reduced to one half, i.e. V = 12.6%. The coefficient does not depend on the contents of specific IgM in a linear fashion, but an antibody change of 1:2 changes it about 1.55 times.
