A Comparative Study of the Hemagglutinating and Skin Sensitizing Activities of Ragweed Sensitive Human Sera

This study was undertaken to determine whether skin sensitizing antibodies are responsible for the capacity of sera from untreated ragweed sensitive patients to agglutinate red cells sensitized with ragweed extract by bisdiazotized benzidine or in tanned cell antiglobulin tests. The procedures used were a) absorption tests employing sensitized red cells; b) inhibition tests with a highly concentrated ragweed extract dialysate; and c) comparison of the hemagglutinating and skin sensitizing titers of different sera. Absorption tests showed somewhat variable results (probably due in large part to the heterogeneity of the system), but in a number of instances complete absorption of hemagglutinating activity was accomplished with no change in skin sensitizing activity. Sera neutralized with a highly concentrated ragweed extract dialysate showed no change in BDB test titers but significant losses of passive transfer activity. No significant correlation was observed between BDB or TCAG hemagglutination test titers and skin sensitizing titers of different sera. Together with recent information from other laboratories, these results indicate that the hemagglutinating activity of sera from untreated ragweed sensitive patients in BDB and TCAG tests is not due solely, if at all, to skin sensitizing antibodies.