Serological and clinical investigation of humidifier fever

Takes your breath away--the immunology of allergic alveolitis

Extrinsic allergic alveolitis (synonym: hypersensitivity pneumonitis) is caused by inhaling antigenic aerosols which induce hypersensitivity responses in susceptible individuals. It is an interstitial inflammatory disease affecting the distal, gas-exchanging parts of the lung, in contrast to allergic asthma where the inflammation is more proximal, affecting the conducting airways. The aims of this review are to describe current concepts of the immunology of this model of lung inflammation, to describe some of the constitutional and environmental characteristics which affect disease susceptibility and development, and to describe topics for prospective study.

Discriminant analysis of symptom pattern and serum antibody titres in humidifier related disease

BACKGROUND

The heterogeneous patterns of symptoms among factory workers exposed to aerosols from contaminated air humidifiers were analysed to assess the association between specific symptoms and the serum IgG antibody response to the humidifier water contaminants, and to test the ability of specific symptoms to predict this antibody response.

METHODS

Symptoms from 88 factory workers were surveyed by a doctor administered questionnaire and compared with their serum IgG antibody titres to humidifier water contaminants quantified by enzyme immunoassay.

RESULTS

The strength of association between individual symptoms and antibody showed that fever, shivering or chills, influenza-like symptoms, or headache were individually significantly associated with the presence and higher titres of antibody. This was also true for those subjects whose symptoms were most pronounced during the first day of the working week. Within each subject's full symptom profile there were significant associations between the description of chest tightness, breathlessness, and wheeze; between headache and influenza like symptoms; between fever and shivering or chills; and between intermittent onset and general tiredness. Discriminant analysis of the full symptom profiles showed that there was maximum information content in five independent parameters, namely, the descriptions of fever, headache, and chest tightness, the timing of their onset, and the readiness to describe miscellaneous symptoms in addition to those in the questionnaire. On the basis of these criteria 72% of subjects could be classified according to their antibody state. Cluster analysis with these five independent parameters described four symptom clusters: one associated with high median antibody levels, one with low, and two with zero median levels. These were, respectively: (1) fever with headache and chest tightness; (2) either no or few symptoms; (3) chest tightness and headache with intermittent onset; (4) headache and miscellaneous symptoms with intermittent onset.

CONCLUSIONS

The association between serum antibody titres and specific symptom patterns may identify different categories of disease which constitute the spectrum known as humidifier related disease, and strengthens the hypothesis that antibody may be involved in the pathogenesis of some components of the disease.

Quantifying serum antibody class and subclass responses by enzyme immunoassay in humidifier-related disease

Antibody activity in the major classes and IgG subclasses against antigens in factory humidifier water was quantified by enzyme immunoassay (EIA) in 88 subjects who were exposed at work to the output from these contaminated humidifiers. Those with work-related symptoms had significantly higher mean titres than those who were symptom free, although values overlapped. The individuals with the highest IgG antibody titres also had the highest titres of IgM and IgA antibody, and these parameters did not discriminate between those with and without symptoms any better than the IgG titre. This was also true for the IgG subclasses where activity was predominantly measured in IgG1. Quantifying the IgG antibody allowed us to demonstrate a significant correlation with years of work exposure (P less than 0.001). There was no significant association between antibody and cigarette smoking, as assessed by smoking history and confirmed objectively by serum cotinine levels. There was a significant correlation with total IgG level (P less than 0.001) suggesting that a non-specific immune enhancement may accompany the specific response. The antibody titres were followed up to 3 years after modification of the humidification systems, and during this time symptoms resolved and the antibody levels progressively fell to undetectable levels. The EIA was adapted to measure antigen at nanogram levels thus providing a rapid test for screening of humidifer water as well as a technique that may help identify the nature of the antigens involved.

[Various forms of humidifier lung]

Clinical and immunological investigations of 15 workers in a repro-printing house revealed a prevalence of 7% for the occurrence of humidifier-lung. Serological sensitization to humidifier water and fungi respectively was found in 73%, fragmentary symptoms in 53%. In comparison to smokers, elevated antibody levels occurred more frequently in nonsmokers (33% vs. 100%). The results are supposed to reflect subclinical stages of disease, but they are not yet of a definite predictive value. Reduction of microorganisms in humidifiers seems to be essential for the prevention of disease.

Precipitating antibodies and positive skin tests in workers exposed to airborne antigens from a contaminated humidification system

Precipitating antibodies and positive skin tests to antigens from a contaminated humidification system in a synthetic carpet yarn plant were tested in a group of exposed (n = 66) and non-exposed (n = 45) workers. The first investigation was carried out in 1979 shortly before hygienic actions to reduce exposure had been taken. In 1981 and 1985 they were repeated. The significant difference between the positive skin reactions and of positive serology (4 or more lines), observed in 1979 between the exposed and non-exposed population, was not found in 1981 and 1985. In 1979 the differences were the most pronounced in the non-smoking individuals. However, even in that category the significant difference disappeared in 1981 and 1985. A positive skin test in 1979 did not increase the chance of having a positive skin test during repeat investigations. In serology this was only the case when the positive criterion was lowered to three or more lines. This study demonstrates that, in the absence of a quantitative analysis of airborne antigens, skin tests and serology may be helpful in obtaining an estimation of antigenic contamination of the air and subsequent sensitization on a group level. However, these tests are less appropriate when used in an individual health surveillance program at this type of nonspecific antigen exposure.