ANALYSIS OF THE ALLERGENIC COMPOSITION OF RAT DUST

Background Allergy to rats is an important occupational health problem . The allergens of rat urine have been well defined but those in rat r oom dust, a potentially important source of inhalant exposure, have no t. Objective To describe the allergens present in rat room dust and to identify a suitable marker protein which may be used to quantify airb orne rat allergen. Methods Dust collected from the air-conditioning sy stem (bulk dust,'bd') and with an air sampler (airborne dust,'ad') wer e analysed by radioallergosorbent test (RAST) inhibition, immunoblotti ng and immunoblot inhibition techniques and comparisons made with hair and urine extracts prepared from adult male Wistar rats. Results Exte nsive crossreactivity was found between the extracts by RAST inhibitio n under different experimental conditions. Dust was more potent as an inhibitor than other extracts. The immunoblotting patterns of both dus ts were similar although 'ad' contained an allergen at 29 kDa not foun d in 'bd'. Forty-two sera from rat allergic subjects were used to iden tify 18 allergens in 'bd'. Three 'major' allergens were found; 100% of subjects had immunoglobulin (Ig)E to a 44 kDa allergen and 74% and 88 % of subjects had IgE with bound to the 20.5 and 17 kDa allergens resp ectively. Immunoblot inhibition experiments identified the 17 kDa dust allergen as alpha(2u)-globulin (Rat nI). Conclusions Rat dust is a co mplex allergenic source. The 17 kDa dust allergen has immunological id entity with Rat nI and is a suitable marker protein for the quantitati on of airborne rat allergen.