Isolation of Ascaris suum components which suppress IgE antibody responses.

An extract from adult Ascaris suum was fractionated on a Sephadex G-200 column and individual elution fractions assessed for their ability to induce or suppress an IgE antibody response in mice immunized simultaneously with a heterologous antigen (ovalbumin). The results showed that, whilst fractions eluted in the first peak suppressed the anti-ovalbumin IgE antibody production, those eluted in the third peak induced a significant anti-Ascaris IgE response. The mixture of the two kinds of fractions resulted in suppression of anti-Ascaris IgE antibodies. The apparent molecular weight (MW) of the first and third peaks was 530,000 and 29,000 daltons, respectively. After delipidation, the extract still retained most of its biological activities. SDS-PAGE of this material showed selective loss of high-MW components when compared to the whole extract. No bands were observed in SDS-PAGE of peak I in contrast to peak III, which displayed several bands. Immunoblots of all these samples showed at least 3 bands above MW 150,000, which reacted with anti-peak I antiserum, in the unfractionated extracts and in peak I, but not in peak III. When the extract was fractionated by affinity chromatography using anti-peak I antibodies as ligands, the immunogenic components were present in the effluent, whereas the suppressive components were recovered in the eluate.