Asthma and Rhinitis Related to Laboratory Rats: Use of a Purified Rat Urinary Allergen to Study Exposure in Laboratories and the Human Immune Response

Using the major rat allergen as a model has made it possible to study both natural exposure and the human immune response to an important laboratory animal. The close correlation between positive skin tests to whole rat urine and IgE antibody to the major urinary allergen in this and previous studies supports the use of this protein as a model rat allergen. Measurements of airborne rat allergen confirm that the maximum levels are higher than those reported with pollen or mite allergens. However, it is possible that exposure to rat allergens is comparable to levels of exposure to cat salivary allergens in houses with cats. The clear implication is that the high levels of exposure are responsible for the fact that a large proportion of exposed individuals develop IgG antibodies. Our results suggest that the prevalence of IgG antibodies (not individual levels) in a group of workers would be a good guide to exposure. This leaves unresolved why some of the individuals who develop IgG ab also develop IgE ab and become at risk for developing asthmatic responses. Only part of this risk is related to atopy. A striking feature of all the studies on animal allergy is the close association between IgE ab and asthma. It appears clear that it is those immune responses that include IgE ab that are a risk factor for asthma. It is not sensible for anyone to remain consistently sick with asthma and continue working with laboratory animals because there are well documented examples of occupational asthma that has not resolved after ceasing exposure. Finally the risk of acute attacks of asthma on exposure to animals must be regarded as a serious health problem both on an individual basis and also in the design and management of research facilities.