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We used a suppressor-cell assay to study a possible mechanism of allergy desensitization. Before specific immunotherapy, blood mononuclear cells from 20 patients with ragweed hayfever failed to exhibit suppressor activity in vitro after stimulation by ragweed antigen E. However, when the 10 patients with allergic rhinitis had been desensitized by injections of ragweed extract, their mononuclear cells specifically suppressed a ragweed proliferative response six and 12 months after desensitization was begun (31 per cent and 48 per cent suppression, respectively). Suppressor mononuclear cells were not detected in 10 control subjects of in 10 patients with ragweed hayfever who were not desensitized. When mononuclear cells taken from treated patients were passed over columns containing insolubilized histamine, antigen-specific suppressor cells that could be activated by ragweed antigen were depleted. These results indicate that antigen-specific suppressor cells, probably bearing histamine receptors, are generated during desensitization to allergy and may be partly responsible for the efficacy of this therapy.

Inhaled steroids and, to a lesser extent, cromolyn confer significant protection against exacerbations of asthma leading to hospitalization. These results support the use of inhaled steroids by individuals who require more than occasional beta-agonist use to control asthma symptoms.

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