Antigenic activity, in humans, of purified low molecular weight fractions of timothy pollen.

Small molecular weight fractions obtained from dialysis of crude timothy pollen extract were shown to carry immunogenic activity in monkeys. These fractions were sequentially purified through gel filtration with Sephadex G-10 and C-M cellulose. Monkeys immunized with these fractions produced almost eclusively skin-sensitizing antibodies which were shown to be of the IgE class, differing in antigenic specificity. These active fractions were assayed in patients allergic to timothy pollen exhibiting an allergic rhinitis. Direct skin tests and inhalation provocation tests were used. The results showed a discrepancy between the skin reactivity and the nasal response to the 3 active fractions. This result can be interpreted as heterogenity of IgE antibodies to small molecular weight fractions contained in crude timothy pollen extract, exhibiting different tissue sensitizing properties.