Inhibition of the passive cutaneous anaphylaxis reaction to Dactylis glomerata pollen allergens by a purified component of this pollen.

By isoelectric focusing a protein fraction of pI 4.6 was isolated from a crude water-soluble extract of Dactylis glomerata pollen (SE). This fraction was neither immunogenic nor allergenic in BALB/c mice. In one week, this protein inhibited the mouse IgE-specific antibodies to the soluble extract as measured by PCA in rats and was therefore called Dactylis inhibitory protein (DIP). Two experimental approaches which lowered IgE anti-SE titer were undertaken. Pretreatment with DIP as well as injection of DIP after the last sensitizing injection with SE resulted in an inhibition of the circulating IgE antibody level to SE. For both experiments the regulation of the immune response touched only the IgE class, whereas the titers of anti-SE IgG, IgM, IgA antibodies were not modified. DIP treatment did not alter the IgE titers, measured by PCA, in the immune response to ovalbumin.