Preliminary characterization of a major allergen of timothy grass pollen.

Previous studies with timothy pollen extracts demonstrated that a low molecular weight dialyzable fraction, antigen D, possessed the allergenic determinant of the major allergen of timothy pollen (allergen B). Bio-gel P-2 gel-filtration of the dialysate fraction resulted in the isolation of a fragment, antigen D3 with a molecular weight near 1000. The relationship of antigen D3 to the antigenic and allergenic determinants of allergen B was evaluated by passive cutaneous anaphylaxis (PCA) in guinea pigs sensitized with rabbit antitimothy sera and by allergen-induced histamine release from monkey lung tissue passively sensitized with the serum of timothy-sensitive patients. These studies demonstrated that 10 units of antigen D3 gave 1) a 70% inhibition of PCA reactions in guinea pigs challenged with allergen B, and 2) a 73% inhibition of allergen-induced histamine release from monkey lung tissue sensitized with timothy reagin and challenged with the crude pollen extract (WST). Although chemical characterization studies of the antigen D3 fragment are still being carried out it appears that the major components fo this fragment are 1) a flavonoid pigment - quercitin, 2) a disaccharide moiety - cellobiose, and 3) the amino acid threonine linked together in an )O-glycosidic type linkage.