[House dust mites at Icelandic farms]. / Maurar í húsryki á íslenskum bóndabaejum.

BACKGROUND: Sensitization to Dermatophagoides pteronyssinus (D. pteronyssinus) occurs in 9% of the Reykjavik population, despite the fact that no Der p 1 antigen has been found in the area. A recent study revealed that sensitized persons more often had a childhood history of work or holiday stay in rural areas than controls. As a follow up we studied the risk of exposure to mites in farmland dwellings. METHODS: In a survey of work-related lung disorders among farmers in the south and west of Iceland, 80 samples of house dust, representing 42 farms, were collected from bedroom mattresses and the floors in living rooms and examined for mites. Treatment of samples was identical with the method used earlier in the Reykjavik investigation (ECRHS II). RESULTS: In contrast to the Reykjavik results, dust from farm dwellings showed a large diversity of mites. Seventeen taxons were found, with Acarus siro and D. pteronyssinus in 13 and 8 farms respectively, but the samples did not show signs that any of the taxons actually had lived or reproduced where they were collected. CONCLUSION: The finding of D. pteronyssinus in farmland dwellings provides a possible explanation of why some Reykjavik citizens might have developed sensitization to this mite, even though cross sensitization to other species of mites could give a false positive reaction to D. pteronyssinus in at least some of those cases. Our observations did not support the idea that the mites were living in the dwellings and an explanation for their occurrence must be sought in the outdoor environment.

Low complement C4B gene copy number predicts short-term mortality after acute myocardial infarction.

BACKGROUND AND OBJECTIVES: Some recent data indicate that risk of death after acute coronary syndrome is under genetic control. Previously, we found that the C4B*Q0 genotype (low copy number of the C4B gene that encodes the fourth component of complement) is strongly associated with morbidity and mortality of cardiovascular diseases (CVD). The +252 G allele of the lymphotoxin-alpha (LTA) gene encoded close to the C4B gene was also reported to be related to CVD-related mortality in an Oriental population. METHODS: The relationship between the copy number of the genes encoding the fourth component of complement (C4A and C4B) and LTA 252 single-nucleotide polymorphism (SNP) on the one hand and mortality after acute myocardial infarction (AMI) was studied in 142 Icelandic patients. The number of the C4A and C4B genes was determined in genomic DNA samples by a newly developed real-time PCR-based method; lymphotoxin-alpha (LTA) +252 A>G polymorphism was determined by PCR-restriction fragment length polymorphism analysis. RESULTS: The C4B*Q0 genotype was found to be strongly associated with 1-year mortality, with a hazard ratio of 3.50 (1.38-8.87) (P = 0.008) (adjusted Cox regression analysis). This association was, however, restricted to ever-smoking patients. By contrast, neither C4A gene copy numbers nor LTA 252 SNP did confer increased risk of mortality after AMI. CONCLUSIONS: This observation indicates that low C4B copy number is a strong risk factor for short-term mortality after AMI in smoking Icelandic patients, whereas LTA 252 G allele is not a risk factor in Caucasian population.