Chemical and immunologic studies of low ragweed pollen extract

Abstract

1. 1. The immunologic activity of three fractions of low ragweed pollen extract, prepared by serial precipitation with alcohol and treatment with chloroform was compared with that of standard pollen extract. 2. 2. Fraction B contained approximately 7 per cent nitrogen and 14 per cent carbohydrate; fraction D contained approximately 5 per cent nitrogen and 58 per cent carbohydrate, and fraction S contained approximately 1.4 per cent nitrogen and 60 per cent carbohydrate and gave a negative ninhydrin test. 3. 3. Standard pollen extract and fractions B and D, but not fraction S were precipitated in vitro by rabbit anti-ragweed serum. Standard pollen extract and fraction B, but not the others, were also precipitated by rabbit anti-fraction B serum. No precipitations were observed with rabbit anti-fraction D serum. 4. 4. Sensitization of guinea pigs to standard pollen extract was produced with each fraction. Sensitization to fraction B was produced with all fractions, except fraction S. Sensitization to fraction D was produced only with fraction D. No sensitization to fraction S could be produced. 5. 5. Studies of untreated ragweed sensitive persons showed that the threshold of sensitivity for skin and conjunctiva to standard pollen extract was lower than to any of the three fractions. 6. 6. Fairly strong evidence is presented indicating that the carbohydrate fraction of low ragweed pollen extract is not a very active antigen since, while it sensitized guinea pigs to whole ragweed extract and elicited positive reactions in untreated ragweed sensitive human beings, it failed to produce precipitins in rabbits. 7. 7. The further the attempts to purify and fractionate the original ragweed pollen extract were carried out, the less striking and consistent were the immunologic reactions observed. Immunologic reactivity diminished with a decrease in the nitrogen content of the fraction.