IMMUNE REACTIVITY OF COW-ASTHMATIC DAIRY FARMERS TO THE MAJOR ALLERGEN OF COW (BDA20) AND TO OTHER COW-DERIVED PROTEINS - THE USE OF PURIFIED BDA20 INCREASES THE PERFORMANCE OF DIAGNOSTIC-TESTS IN RESPIRATORY COW ALLERGY

Background Cow dust is one of the most important inducers of occupatio nal allergic diseases in Finland. For example, in 1991 it accounted fo r almost 40% of the new occupational asthma cases. Objective This stud y compares the performance of the purified major cow allergen (BDA20) and crude bovine epithelial extract (BEA) in diagnostic tests and exam ines the role of milk allergy-associated bovine proteins (bovine serum albumin, alpha-lactalbumin, beta-lactoglobulin, casein) in respirator y cow allergy. Methods The humoral responses of cow-asthmatic and heal thy farmers to the various components of BEA were analysed with sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and imm unoblotting. The levels of specific IgE and IgG antibodies were quanti ficated with enzyme-linked immunosorbent assays (ELISAs). The cellular responses were analysed with antigen-specific lymphocyte proliferatio n tests. Results The specific anti-BDA20 IgE measurement was found to be best in distinguishing between the asthmatic farmers and their heal thy colleagues. It proved possible to determine a cut-off value that g ave the analysis a specificity and sensitivity of 100%; the distinctio n between the two groups was highly significant (P < 0.0001). In the l ymphocyte proliferation analysis, cow asthma was more closely associat ed with reactivity to BDA20 than to BEA. In the measurement of anti-BD A20 and anti-BEA IgG antibody levels, considerable overlap between the groups was observed, suggesting that these antibodies are not directl y involved in cow allergy. When proteins associated with milk allergy were used as test reagents, no statistically significant differences c ould be observed between the groups, except for anti-casein IEE antibo dies the level of which, however, overlapped considerably between the farmer groups. Conclusion These findings suggest that purified BDA20 i s better than BEA for diagnosing cow asthma and that proteins associat ed with milk allergy are of only marginal significance in this disease .