Natural immunity to dust mite (Dermatophagoides farinae) antigen was assessed in a population of 63 adults with a clinical diagnosis of chronic asthma. Immunity was determined by measuring immediate hypersensitivity to an intracutaneous injection of dust mite antigen, mite-specific serum IgG concentrations using a double antibody ELISA, and mite-specific serum IgE concentrations by RAST. Using these tests, 68% of the asthmatic patients exhibited a positive skin test; 38% had elevated concentrations of mite-specific IgE, and 63% had elevated concentrations of mite-specific IgG. In contrast, when analyzed individually, these tests were positive in only 10 to 11% of normal subjects or patients with chronic obstructive pulmonary disease. Only 10% of asthmatics had elevated serum concentrations of mite-specific antibodies of the IgG4 subclass. The asthmatic patients could be subdivided into 4 groups based on their immunologic reactivity to dust mites; 24% of the patients had elevated concentrations of mite-specific IgG in the absence of allergic reactivity to mites (skin test). A second subgroup (27%) exhibited allergic reactivity in the absence of elevated concentrations of mite-specific serum IgG. A third subgroup (41%) consisted of patients who exhibited both allergic reactivity and elevated IgG concentrations. The smallest subgroup (8%) consisted of patients with no measurable immunity to mites. In total, 94% of the asthmatic group exhibited a positive immune response to at least one of the dust-mite-specific tests, whereas only 26% of the normal subjects could be considered to be immune using the criteria of a positive reaction in at least 1 of the 3 tests.(ABSTRACT TRUNCATED AT 250 WORDS)