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Biomedical subjects

J Merrett

Publications and source records attributed to J Merrett.

At least 19 recordsLinked to original sources
PubMed1997

Feather mites are potentially an important source of allergens for pigeon and budgerigar keepers.

BACKGROUND: Previous studies on allergy to feathers have not addressed whether organisms living on feathers (mites, lice, moulds) are a source of allergens. OBJECTIVE: To investigate whether feather mites produced allergens of clinical relevance to bird keepers. METHODS: We examined serum IgE responses of 96 pigeon breeders to an extract of feather mites from pigeons (predominantly Diplaegidia columbae), using Western blotting, specific IgE assay using AlaSTAT EIA and RAST inhibition. RESULTS: Feather mites are a major source of soluble proteins derived from feathers, accounting for up to 10% of the total weight of the feather. Forty-three sera had a negative score (0) for anti-feather mite IgE, 27 were weakly positive (1-2) and 26 had strongly positive scores (3-4). Fewer pigeon breeders with scores > or = 3 were asymptomatic than those with negative scores (12 versus 40%), more had late onset symptoms (with or without early onset symptoms: 77% versus 44%) and had IgE antibody against house dust mite (89% versus 23%). Western blotting of eight sera against the extract of Diplaegidia columbae revealed 20 IgE-binding components ranging from 22 to 200 kDa. A high diversity of components was recognized by each serum: arithmetic mean 7 (range 2-14). RAST inhibition indicated feather mites had species-specific epitopes as well as ones that cross-reacted with Dermatophagoides pteronyssinus. CONCLUSION: Strongly-positive AlaSTAT scores to pigeon feather mite were associated with allergic symptoms of late onset in pigeon breeders. We conclude that feather mites are a major source of clinically-relevant allergens for pigeon breeders.

Allergens↗
PubMed1988

Infant feeding and allergy: 12-month prospective study of 500 babies born into allergic families.

This investigation studied 487 babies for symptoms of allergic disease during their first year of life. Because of their positive family histories all the babies are at high risk of becoming allergic. The babies were randomly divided such that cows' milk was deliberately withheld from one group; infants in this group were fed with a soya substitute where required. No benefit resulted from withholding cows' milk, indeed symptoms were more usually associated with this group. Breast feeding, even for a short period, was clearly associated with a lower incidence of wheeze, prolonged colds, diarrhoea, and vomiting. It seemed that the duration of breast feeding was less important than whether or not the child had been breast-fed at all. Wheezing was both more common among boys than girls (P less than .05) and if the mother was a smoker. Other environmental features related to wheezing were social class, month of birth, lack of breast feeding, exposure to dampness, mould and coal fires, but not to domestic pets nor to the numbers of mites found in bedding and carpets. Mite exposure was, however, associated with prolonged colds. Eczema was the only allergic symptom not positively associated with any environmental factor; moreover, it was neither associated with a lack of breast feeding nor with inclusion of cows' milk in the diet. Eczema was associated with the incidence of positive skin prick tests and IgE antibodies to egg white. IgE and IgG4 antibodies were estimated at birth (mothers' and cord bloods) and 3 and 12 months later.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

Phadiatop--a novel IgE antibody screening test.

The Phadiatop test, which is based on a multi-allergen allergosorbent, proved to be a test that is simple to perform in the laboratory and produces reliable results. When compared with the more conventional RAST atopy screening test for grass, mite and IgE antibodies it produced similar results, except in those rare instances of patients who were RAST-positive only for moulds where the Phadiatop test was decidedly superior. The Phadiatop test disc contains only inhalant allergens and so it could not be used for screening infants and very young children whose IgE response, if any, is probably limited to foods.

Evaluation Studies as Topic↗
PubMed1984

Immunologic studies in allergen-induced late-phase asthmatic reactions.

We have measured plasma histamine, serum neutrophil chemotactic activity (NCA) and complement (C3 and C4) over a 24-hour period in patients experiencing either early- and late-phase (dual) or single early asthmatic reactions to inhaled allergens. There was a significant biphasic elevation in plasma histamine, which paralleled the fall in forced expiratory volume in 1 sec in 10 patients with dual responses, whereas in seven subjects with single early reactions, only a single early increase in histamine concentrations was observed. In general, in the individual subjects, the changes in plasma histamine paralleled both the elevations in serum NCA and the decreases in forced expiratory volume in 1 sec. By gel filtration on Sephacryl S-400, anion exchange chromatography on DEAE Sephacel, and chromatofocusing with Polybuffer Exchanger 94, the major NCA of both the early and the late reactions was associated with proteins having an estimated molecular size of 600,000 daltons, an elution from DEAE Sephacel at 0.15M to 0.30M of NaCl (pH 8.1), and a pI of approximately 6.5. There were no appreciable changes in serum C3 and C4 up to 24 hr after challenge in subjects with late-phase responses. The patterns of asthmatic response were not related to either the total or allergen-specific serum IgE or IgG4 concentrations. These results support the view that mediators of hypersensitivity participate in late-phase as well as early asthmatic reactions.

Adolescent↗
PubMed1984

Immediate hypersensitivity, IgE and asthma.

Twenty-one asthmatic and twenty-two non-asthmatic children and nine asthmatic adults from two different rural areas of Tanzania, and eight asthmatic children from Dar-es-Salaam were surveyed by questionnaires, skin testing and the measurement of serum IgE. Asthma was significantly commoner in female rural children (four males, fifteen females). The rural asthmatic children apparently had less skin reactivity (in seven of nine tests) and lower specific (in two of four tests) and total serum IgE than age-, sex- and village-matched controls. This pattern of asthma in rural children in the tropics represents a different type of asthma from that found in temperate zones. In contrast, the adult rural asthmatics and the urban children seemed to have the pattern of increased skin reactivity and serum IgE found in asthmatic patients from temperate climates.

Asthma↗
PubMed1984

Total and specific IgG4 antibody levels in atopic eczema.

Total IgG4 and IgG4 antibody levels specific for 10 allergens (three inhaled and seven ingested) were measured by radioimmunoassay of sera taken from three groups of adult patients: (1) 32 cases of atopic eczema, (2) 28 cases of respiratory allergy and (3) 156 normal volunteers. In all three groups IgG4 antibody activity was mainly directed against common foods, and generally the group with atopic eczema had higher total and specific IgG4 levels than the cases of respiratory allergy, who in turn had higher titres than the normal group. There was within each group a tendency for men to have more total IgG4 than women and the difference was statistically significant among the normals. There was evidence of an IgG4 restricted response in atopic eczema because despite the group's elevated total IgG4 its total IgG4 remained within normal limits. Furthermore specific IgG4 was correlated with the corresponding specific IgE level in five of the 10 allergens examined. These results are generally consistent with the view that IgG4 levels are raised in cases of atopic eczema due to prolonged exposure to an allergen which initiated an IgE response.

Adolescent↗
PubMed1983

A community survey of IgG4 antibody levels.

Precise and specific radioimmunoassays have been developed to quantify IgG4 and IgG4 antibodies. A community survey has demonstrated that men have significantly higher total serum IgG4 levels than women: geometric mean values of 0.581 mg/ml versus 0.302 mg/ml. This sex difference was extended to total IgE values. Circulating levels of IgG4 antibodies against foods, especially egg and milk, were normally higher than those against the three most common U.K. inhalant allergens--grass pollen, house dust mite and cat epithelium.

Adolescent↗
PubMed1983

Food related antibodies in headache patients.

Highly sensitive and specific methods for assaying IgE and IgG4 for antibodies in serum have been developed in order to test a recent suggestion that food allergy is a major cause of migraine. Sera were collected from 208 adults--74 with dietary migraine, 45 with non-dietary migraine, 29 with cluster headache and 60 controls. No significant differences were identified between any of the groups with the one exception that cluster headache patients had significantly raised levels of total serum IgE: this difference may be explained by the high proportion of smokers. Mean IgG4 titres to cheese, milk and chocolate were very similar in the dietary and non-dietary migraine patients and the control subjects, though lower in the cluster headache patients. There was, therefore, no evidence that the food intolerance often associated with migraine headaches is associated with a conventional allergic mechanism.

Cluster Headache↗
PubMed1980

Assessing the value of skin prick tests.

Skin test materials vary in their potency and specificity. Although 3 mm reactions are often regarded as diagnostic of a type 1 allergy, a study based on 100 allergy clinic patients with food intolerance showed that thirteen out of fifteen patients with a 3 mm reaction to common inhalant allergens had no RAST-detectable allergen-specific IgE. Three millimetre reactions were significant for milk and egg extracts. Food intolerance was clinically demonstrable in six out of seven patients giving a 4 mm skin reaction and in ten out of thirteen with a 3 mm reaction. There was, however, a "clinically false positive" reaction of 3 mm or more in 3.8% of allergy clinic patients for milk and 2.8% for egg. In fifteen out of nineteen patients with a clinical diagnosis of fish allergy, the diagnosis was supported by a skin test reaction of 5 mm or more. However, seven patients with no history of intolerance to fish gave a 4 mm reaction to the same extract. Reactions of less than 5 mm were thus unhelpful clinically.

Animals↗
PubMed1980

Circulating IgE levels in the over-seventies.

In a normal population aged over 70 years the geometric mean IgE value of 30.6 u/ml was not significantly different from that obtained previously in a similar epidemiological survey of a population aged 20-44 years. However, in the older population we have noted a significant sex difference-38.6 u/ml for males against 27.2 u/ml for females-which was only apparent in the atopic subjects of the younger population. There have been some other reports that IgE levels decrease with age, and possible reasons for these differences with our own results are discussed.

Adult↗
PubMed1980

Screening for IgE-mediated allergy.

Sera from 425 patients were analysed with Phadebas RAST reagents against a panel of 19 allergens and the most commonly positive results were to grass pollen, Dermatophagoides pteronyssinus and cat epithelium. Of the 275 sera RAST-positive to any allergen, 261 were positive by a RAST technique which used a mixture of the three most common U.K. allergens; the remainder were usually positive to a mould. We conclude that 1) when a positive result is obtained after screening by the mixed-allergen RAST and a representative mould RAST, then other positive RAST results are possible, but that the extent of the investigation can be guided by a knowledge of the total serum IgE level and a computer-based history analysis; 2) when a mixed-allergen RAST and a representative mould RAST is negative, then a more specified RAST including all 19 allergens used in this investigation will be negative; 3) a positive mixed-allergen RAST result is likely to be associated with a total serum IgE level over 40 U/ml and a positive symptom pattern score derived from the computer-based history analysis.

Adolescent↗
PubMed1980

Immunological investigations in vernal eye disease.

A group of patients with vernal disease was investigated for serum IgE levels, specific antibody to external allergens in serum and tears, and the frequencies of the HL-A antigens. Biopsies taken from the conjunctiva were examined by means of light and electron microscopy for the presence of mast cells and other inflammatory cells. Serum IgE was elevated in 75 per cent of the patients, all of whom demonstrated positive prick tests to common allergens and specific antibody in their serum using the radio-allergosorbent test (RAST). Specific antibody was also demonstrated in tears using the same technique. The distribution of the HL-A antigens showed no difference in frequency when compared with controls. Conjunctival biopsies demonstrated numerous mast cells, the more superficial of which were degranulating in active disease. In control biopsy material, mast cells were densely packed with granules. The clinical manifestations in vernal disease together with the infiltration of the tarsal conjunctiva with many types of inflammatory cell, are possible caused by mediators which are known to be produced by degranulating mast cells when they are stimulated by allergens.

Adolescent↗
PubMed1980

Food allergy and intolerance in 100 patients---local and systemic effects.

One hundred patients who reacted adversely to one or more specific foods were studied. In 93 the food induced symptoms included asthma, eczema, angioedema, urticaria, rhinorrhoea, or a combination of one or more of these with gastrointestinal symptoms. The remaining seven had gastrointestinal symptoms only. The diagnosis of food allergy was made on the on the basis of a definite, immediate allergic reaction to specific foods or a reaction that was suggestive of allergy, supported by a corresponding positive skin prick or radioallergosorbent test. In the absence of such evidence, the less specific diagnosis of 'food intolerance' seemed preferable. Test materials appeared to differ in their diagnostic usefulness. A high proportion (c. 75 per cent) of patients who were intolerant to egg, fish or nuts had positive test results. In contrast, only 30 per cent of patients with milk intolerance had positive tests, suggesting inadequate test methods or a non-allergic cause for many patients' milk intolerance. Nevertheless, five milk intolerant patients with negative tests had milk-induced asthma.

Adolescent↗
PubMed1979

Epithelial or dandruff allergen for the diagnosis of dog allergy by RAST?

When used for screening by the RAST technique, dog epithelium provided too few positive results (29.2%) compared with dog dandruff (58.8%), cat epithelium (53.6%) and horse dandruff (52.2%). However, dog dandruff can provide an unexpectedly high incidence of positive RAST results (45.2%) in sera from patients with an allergic history to cat or horse, but not to dog. Dog dandruff allergens were found to cross-react with some cat or horse serum proteins in about 25% of such patients. We conclude that dog dandruff is preferable to epithelium for screening by the RAST technique, but if emotional issues involving a family pet arise then confirmation by a trial separation is likely to be more convincing than a provocation test with a possibly non-specific allergenic extract.

Allergens↗