COCKROACH ALLERGEN AND ASTHMA (John Tsongalis)
A recent study done by researchers affiliated with the National Cooperative Inner-City Asthma Study found higher incidence of asthma among inner-city children upon exposure to cockroach allergen. The study involved data from eight different inner-city areas from across the country taken from families that were deemed socioeconomic minorities. Factors taken into consideration for the study were family history of asthma, number of asthma related hospitalizations and doctor visits over the course of one year, and the effect of cat and dust mite allergen in the environment of the patients in comparison to cockroach allergen.
Results from the study showed that 50% of the living areas researched(i.e. bedrooms) contained high levels of cockroach allergen. According to the study, a high level of cockroach allergen was that accounting for 85% of the total allergen level measured in the room. In these cases the levels of cat allergen and dust mite allergen were negligible, particularly since the subjects had been skin tested for hypersensitivity to the cockroach allergen. These children had a higher incidence of asthma related hospitalizations and doctor visits compared to other children in the study not exposed to these levels of allergen.
The allergen content in the study was determined from dust collected from the bed linings and carpet, using a monoclonal antibody based ELISA. Skin tests were administered to determine hypersensitvity to each of the three allergens used in the study. (1)
One study has determined the allergic component of the cockroach allergen to be a 23 kiloDalton protein which is a glutathione S-transferase protein of Blatella germanica. The allergen was purified from cockroach body extracts and expressed as a recombinant protein in E. coli using a plasmid vector. The recombinant protein was used in skin tests on patients allergic to cockroach allergen and showed positive tests with allergen concentrations as low as 3 pg. The experimental results from this study also concluded that glutathione S-transferase caused an IgE response and is instrumental in causing asthma in patients allergic to cockroach allergen. (2)
Another study done by Matthias Wjst in Germany focused on discovering the genes responsible for causing asthma. This study looked at gene families that would be good candidates for causing the disease by looking at microsatellites, which are polymorphic gene markers associated with gene families. These markers help to determine the location of a gene that is potentially responsible for causing disease. In his study, Wjst implicates certain genes involved in allergic reaction as those which might be involved in causing asthma. Among these genes are IL-4, FceRIb, TCRa, and HLA DR I. In the case of an allergic reaction, the allergens will be presented by Class II MHC to the TCR on the T helper cell. This interaction will signal the cascade of events leading to the production of IL-4 by the T lymphocyte which in turn will increase the expression of IgE by B cells due to the induction of class switching from the cytokine. (3)
- Rosenstreich, DL et al. The role of cockroach allergy and exposure to cockroach allergen in causing morbidity among inner-city children with asthma. New England Journal of Medicine May 1997 May 8;336(19): 1356- 1363.
- Arruda LK, et al. Induction of IgE antibody responses by glutathione S-transferase from the German cockroach (Blatella germanica). J Biol Chem 1997 Aug 15: 272(33): 20907-20912.
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