[Determination of antitoxoplasma IgM antibodies using the ELISA method]. / Stanovení antitoxoplazmických protilátek IgM metodou ELISA.

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.

[Antitoxoplasma serum--derivation of the national standard (ELISA)]. / Antitoxoplazmické sérum--odvození národního standardu (ELISA).

When assessing the content of specific antibodies in serum there is tendency to abandon the specification expressed as dilution and use more reproducible data, i.e. international units. To this end it is necessary to derive from the international standard the national standard according to which positive control sera in diagnostic sets, produced by SEVAC can be described in international units. In pooled positive human serum recommended as the national standard and in the international standard first the parallel course of the dose/response curve was tested. Then both sera were repeatedly compared: into a close dilution series of the national standard one dilution of the international standard was included and in both sera the dilution with same response was found (by optic density) and thus the activity of the suggested national standard was assessed as 2400 units/ml. The author discusses also the recommended routine procedure for expressing the activity of the examined sera in international units.