Possible indirect binding of IgE in house dust RAST

House dust subfractions obtained in the course of purification exhibit increasing skin reactivity in allergic patients, which runs parrallel to both complement-consuming and RAST-binding capacity. Working with highly purified house dust allergen in RAST, the correlation with clinical parameters for house dust allergy was found to remain poor. In a large group of sera a significant statistical correlation was found between total IgE and allergen-binding IgE. Ultracentrifugation experiments demonstrated that IgE binding to allergen in RAST occurs in complex with an unidentified serum protein. These results suggests that IgE binding in house dust RAST is indirect and is mediated by another serum factor.