In this review outlines are given on various types of enzyme immunoassay. The applications to such enzyme immunoassays, especially ELISA, are dealth with in detail. It is concluded that these techniques have high sensitivity and will be suitable in due course as routine laboratory tests.

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syNopsIs A new test for the detection and measurement of toxoplasma antibody is described. Test sera are reacted with antigen-sensitized wells in micro-haemagglutination plates. Any attached antibody is shown by the addition of an enzyme-labelled antiglobulin followed by assay of the enzyme reaction with its substrate. The test is easy to carry out on a large scale, and there is a positive correlation between the results and dye test and haemagglutination test titres.The diagnosis of toxoplasmosis is not easy and is usually based on the critical assessment of one or more serological tests. The dye test (Sabin and Feldman, 1948), indirect immunofluorescence (Kelen et al, 1962), and passive haemagglutination (Jacobs and Lunde, 1975) are the tests most frequently employed. Karim and Ludlam (1975) London were tested by the dye test (Sabin and Feldman, 1948), by passive haemagglutination (Jacobs and Lunde, 1975), and by the microenzyme linked immunosorbent assay (MICRO-ELISA) described below. These sera came from clinically suspected cases of toxoplasmosis and 16 of them, with dye test titres over > 1/1024, were from typical lymphadenopathy cases. MICRO-ENZYME-LINKED IMMUNOSORBENT ASSAYThe enzyme-linked immunosorbent assay (ELISA) of Engvall and Perlmann (1972) with the modification (MICRO-ELISA) of Voller et al (1975a) was used. The principle of the assay is described in figure 1. For toxoplasmosis the test was carried out as follows: 1 The wells in microhaemagglutination plates (COOKE MICROTITER M29 AR') were sensitized with the toxoplasma antigen, diluted in 0-05M carbonate buffer, pH 9-6, overnight at + 4°C. The plates were then given three washes each of 3 minutes in phosphate buffered saline (PBS) containing 0-05 % Tween 20 and were shaken dry. 2 0 3 ml of the diluted serum was added to each well and incubated for 2 hours at room temperature.The plates were washed as before in PBS/Tween and were shaken dry. 3 0 3 ml of the diluted antiglobulin conjugate was added to each well and incubated for 3 hours

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