Indirect immunofluorescence in toxoplasmosis: frequency, nature and specificity of polar staining.

In the indirect immunofluorescence test ant the Remington test for Toxoplasmosis of some sera, a polar fluorescence of the parasite has been observed. This "Polar Factor" is not observed in umbilical cord blood and in sera of children less than 6 months old, but has a relative high frequency in sera of adults. The detection of the factor depends on the nature of the used antigen. With sucrose gradient centrifugation, anti-IgM immunofluorescence, 2-mercaptoethanol-treatment and selective adsorption of sera, we could demonstrate that this factor is a non-specific IgM.