Studies on Alternaria allergens. III. Effect of Alternaria tenuis on the humoral response to three T cell-dependent antigens in rats.

The effects of an extract of the saprophytic mold, Alternaria tenuis (AT-CE) on the humoral response to a ragweed allergen extract (DWSR), ovalbumin and sheep red blood cells (SRBC) was investigated in female Wistar rats. Animals pretreated with 100 micrograms or 2 mg AT-CE showed enhancement (p less than 0.05) in the reaginic response (IgE antibody) to DWSR at 25 and 18 days postimmunization. On the other hand, animals posttreated with AT-CE showed substantial reduction in anti-DWSR IgE antibody response. Contrasting results were obtained when ovalbumin was used as an immunizing antigen. There was a remarkable enhancement in the reaginic response to ovalbumin in rats pre- or posttreated with 10 micrograms of AT-CE. Pretreatment with AT-CE did not affect the hemagglutination titers to ovalbumin, while posttreatment with 100 micrograms or 1 mg AT-CE increased the hemagglutination titers of IgM antibody. There was a significant reduction in hemagglutinin, and hemolysin titers to SRBC in animals pretreated with all concentrations of AT-CE; at day 21, suppression was noted in animals pre- or posttreated with all concentrations of AT-CE. On the other hand, greatly increased hemagglutination titers were found in animals posttreated with 100 micrograms or 1 mg AT-CE. Hence, enhancement and suppression can both occur depending on the dose and time of administration of AT-CE together with the nature of the immunizing antigen.