The biological activity of a ragweed arabinogalactan. I. Galactose specificity of in vitro and in vivo effects.

A mouse antiserum to ragweed arabinogalactan (AGRg) agglutinated rabbit red blood cells coupled to AGRg by bis-diazotized benzidine. The antibodies to AGRg could be absorbed out with a yeast phosphogalactan but not with a yeast phosphomannan. A beet araban was also ineffective. Whole pollen grains from ragweed, timothy, wheat, barley and rye as well as commercial pollen extracts such as ragweed, timothy, sage and maple produced complete inhibition of haemagglutination. These studies suggest that cross-reactions between unrelated pollens previously reported may have been due to the presence of arabinogalactans in the materials employed. The permeability-enhancing effects of AGRg in mice could be completely inhibited by D-galactose, D-fucose or by galactose containing oligosaccharides. The stereochemical specificity of this inhibition suggests, but by no means proves, that the effects of AGRg are due to its interaction with natural antibody.