Studies on the immunological relationship of ragweed pollen antigens E and Ra.3

Abstract

This study compares the allergenic and antigenic activities of ragweed pollen antigens Ra.3 and E using the human leukocyte histamine release assay. Leukocytes from 23 antigen E-sensitive patients were challenged separately with varying concentrations of Ra.3 and E. Six were unresponsive to Ra.3, although the same cells released 60 to 100 per cent histamine on challenge with antigen E. The leukocytes of 16 patients gave maximal release of 50 to 100 per cent with Ra.3. Leukocyte sensitivity to Ra.3 relative to E ranged from 0.1 to 10 4 and demonstrated little or no allergenic cross-reaction between the 2 antigens. Skin tests on an additional 19 patients confirmed this pattern. Leukocytes were challenged separately with mixtures of each allergen and dilutions of human antisera to antigen E (α-AgE) and water-soluble ragweed (α-AgWSR). Whereas α-AgWSR and α-AgE were equally inhibitory to E-induced histamine release, only AgWSR effectively inhibited Ra.3-induced release. Rabbit antiserum to Ra.3 and AgE in most patients inhibited the homologous allergen and demonstrated little or no cross-reactivity. In 2 patients, however, anti-AgE inhibited Ra.3-mediated histamine release while the homologous antiserum was inactive. We conclude that antigens Ra.3 and E are antigenically and allergenically distinct.