To further study the immunology of insect hypersensitivity, we identified and partially characterized the principal allergens in whole body German cockroach (WBGCR) (Blattella germanica) and compared this extract to whole body antigens prepared from other insects. WBGCR extract was fractionated over a calibrated Sephadex G-200 column; peak allergenic activity was contained in fraction 3 (GCR3), containing components with apparent molecular weights ranging from 12,500 to 75,000 daltons. The antigenicity, allergenicity, and specificity of GCR3 components were tested by using rabbit antisera raised to GCR3 or true armyworm (Pseudaletia unipuncta). Radioimmunoassay, cross-inhibition and immunoblot studies revealed, particularly in the IgE system, that GCR3 contained an allergen with a pI of 6.7 and MW of 36,000 daltons that was unique to WBGCR extracts and not present in other insect species, including true armyworm, caddis fly, lakefly, yellow jacket, or honeybee. This GCR3 component may represent a specific marker for the diagnosis of cockroach hypersensitivity in an insect-sensitive population of individuals.

Background: Cockroach allergy occurs frequently in asthmatics in urban areas, where the level of cockroach infestation is usually high. The prevalence of cockroach allergy, as well as the effect of associated factors on cockroach sensitisation in Nigeria is largely unknown. Objective: To determine the prevalence of cockroach allergy in asthmatics in Lagos. Design: A prospective case-control study. Setting: Medical outpatient department of the Lagos University Teaching Hospital, Lagos, Nigeria. Subjects: Two hundred and two patients with confirmed bronchial asthma and one hundred non-asthmatic control subjects took part in the study. Intervention: The cockroach allergen was administered on all the subjects using skin prick technique. Main outcome measures: The provocation of a skin reaction (wcal) fifteen minutes after administering the cockroach antigen.Results: Amongst the asthmatic patients 90 (44.6%) had positive skin tests to the cockroach allergen, compared to nine (9%) of the control subjects. There was a male preponderance of cockroach sensitivity amongst the asthmatic patients even though the difference between both sexes was not significant. Other highlights of the study included the fact that cockroach sensitivity was related to age, duration of asthma, nocturnal asthmatic attacks, frequency of attacks, and the levels of infestation. There was an insignificant relationship between cockroach sensitivity and the location of residences as well as the income status of the respondents. Conclusion: There is the need for more studies on cockroach allergy in asthmatics in our environment.provoke clinical reactions as contactant, inhalant, injectant and ingestant allergens. The whole body, faecal extracts, casts and egg shells of the cockroach have been isolated and found to be important sources of allergens in the induction and exacerbation of bronchial asthma(10,11). The cockroach produces antigen specific IgE which not only provokes a hyper sensitivity reaction but can also produce severe allergic bronchial asthma(12). The immunological profile of the cockroach was also elucidated by Helm et al(13) who isolated the cockroach fraction III a heterogeneous protein containing fractions I and II which had been identified by earlier workers(11).The primary focus of this study was to evaluate the prevalence of cockroach hypersensitivity amongst asthmatics in an urban city like Lagos, whilst looking at the association between this entity and other correlates like age, sex, socio-economic status and the patient's environment to which cockroach allergy has been found to be related. (10,(14)(15). The relationship between the history of exposure to cockroaches and the occurrence of positive skin test results to the cockroach allergen was also evaluated.

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