BRITISH SOCIETY FOR ALLERGY AND CLINICAL IMMUNOLOGY

Further immunochemical studies ofthe two major allergenic components of rat urine, viz. The pre-albumin and the a2-euglobulin (Longbottom, 1981) has shown them to be closely related proteins. Amino acid analyses were very similar for both proteins, aspartic acid, glutamic acid, glycine, valine and leucine occurring in the highest amounts. Protein and carbohydrate (CHO) determination, however, showed that the pre-albumin had a higher CHO content than the a2-globulin, i.e. 5-4 compared with 1 2%, lower protein content, i.e. 72 compared with 86%, therefore giving protein/CHO ratios of 13:1 and 71:1 respectively. This increased CHO content may account for the slightly higher molecular weight of the pre-albumin. It was previously shown that the a2-euglobulin (pi values 5 4, 56 and 5-8) was antigenicaliy, partially cross-reacting with the pre-albumin (pi values 4-5 and 4-6) and by developing a new method, employing crossed immunoisoelectric focussing with autoradiography (Longbotton, J. L., to be published) it was possible to show that all the isoforms of both components were equal in their binding of specific IgE of rat allergic sera. Immunological studies for alternative sources for these proteins showed that the a2-euglobulin was present in extracts of both rat liver and kidney, whereas the pre-albumin could be detected in saliva, dander, faeces (dry) and rat dust (see later presentation), but neither component could be detected in rat serum.