Development of electron spin resonance radical immunoassay for measurement of airborne orchard grass (<Emphasis Type="Italic">Dactylis glomerata</Emphasis>) pollen antigens

We have developed a highly sensitive method for the measurement of airborne orchard grass (Dactylis glomerata: Dac g) pollen antigens using an electron spin resonance (ESR) radical immunoassay. In this immunoassay, the lowest detectable level of Dac g antigen in a sample is 0.1 arbitrary unit; the amount of Dac g antigen in single pollen grains was found to be as 1.84 units. Thus, Dac g antigens can be detected in amounts of 1/20th of that contained in the grain. This immunoassay enables early detection of grass pollen antigens. Such information may be useful for patients with grass pollinosis, especially for those who show symptoms when only low levels of the pollen antigens are present in air. In this study, minor amounts of Dac g antigen (cross-reactive antigens) were detected in late March, after which the levels gradually increased. The levels were detected to be 10 units/m³ until the middle of May and then increased after blooming of orchard grass. High levels were maintained until the middle of June. Some patients who suffer from grass pollinosis show symptoms in late April and early May, when the airborne Dac g antigen levels were found to be 5–10 units/m³.