IN-SITU LOCALIZATION OF A HIGH-MOLECULAR-WEIGHT CROSS-REACTIVE ALLERGEN IN POLLEN AND PLANT-DERIVED FOOD BY IMMUNOGOLD ELECTRON-MICROSCOPY

Background: A high molecular weight (60 kd) allergen has been recently identified as a cross-reactive moiety in pollen and plant-derived foo d. While the cross-reactive allergen has been characterized by immunoc hemical techniques, little is known concerning its biologic properties . Objective: In this investigation we studied the in situ localization of the 60 kd cross-reactive allergen in tree, grass, and weed pollen, as well as in plant-derived food (apple and celery). Methods: A monoc lonal antibody (3A4) that was raised against the major mugwort pollen allergen, Art v 1, was used to demonstrate the presence of related all ergens in nitrocellulose-blotted pollen and plant-food extracts. The t issue localization of the cross-reactive allergen was investigated by immunogold electronmicroscopy. Results: Monoclonal antibody 3A4 recogn ized IgE epitopes of the 60 kd mugwort allergen and cross-reacted with moieties of comparable molecular weights in birch and timothy grass p ollen, as well as in apple and celery extracts. In pollen and plant-de rived food the allergen could be localized intracellularly in ribosome -rich areas in the mitochondria and the nucleus. No labeling was obser ved in the pollen or cell walls or in organelles that are engaged in s torage (e.g., starch granules and lipid particles). Conclusion: Tree, grass, and weed pollen, as well as plant-derived foods, contain a high molecular weight Art v 1-cross-reactive allergen that maps to similar cell compartments.