The fluorescent antibody technique in the estimation of immunity in patients infected with Plasmodium malariae

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Abstract
Investigations were performed in 15 psychiatric patients therapeutically infected with Plasmodium malariae (strain VS) in whom antibody titers in the blood serum were determined by the indirect fluorescent antibody staining technique. The results were compared with clinical findings, im-munobiological data and gammaglobulin levels as determined by paper electrophoresis. These investigations indicate that the negative phase of the primary response to the antigenic stimulus lasts 4- 6 days after the onset of parasitemia. After primary stimulation the immunological response varies according to the persistence and intensity of the antigenic stimulus. In the case of prolonged antigenic stimulation followed by a state of parasitic tolerance (symptomless parasitaemia), antibody titers ranged from 2000 to 3000, at 596 and 827 days after the onset of parasitemia. In the re-inoculated patients, the secondary immunological response was characterized by increased antibody titres, attaining figures of 3000 to 5000. In one case (V.C.) antibodies were demonstrable at a titer of 1000, 665 days after the subsidence of parasitaemia. The fluorescent antibody technique is a highly valuable test for demonstrating and assaying immuno-biological response in malaria. The test was negative in non-immune controls and in patients tested before inoculation of the parasite. It was likewise negative in patients re-inoculated with strain VS, who displayed no clinical symptoms of malarial infection, because the secondary infection had been preceded by efficient chemopro-phylaxis which suppressed the antigenic stimulus.

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