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Endotoxin and Asthma

In their recent study on endotoxin exposure as a risk factor for asthma, Thorne and colleagues found a relation between floor dust endotoxin levels and diagnosed asthma, asthma medication, and wheezing among adults (1). While I agree with the authors' conclusion that the symptomatology reflects an inflammatory response that is more pronounced among those with an allergy, I would caution against any conclusions concerning causality. In house dust, endotoxin is only one of many microbial cell wall agents (MCWAs) with biological effects; other examples are mycobacterial lipoglycans, lipoteichoic acid, peptidoglycan, N-acetylmuramic acid, and lipoarabinomannan (2).

Many MCWAs have inflammatory properties. Although the MCWA (1-3)--D-glucan is not inflammatory by itself (3), it reflects the presence of mold cells, which cause a neutrophilic inflammation akin to endotoxin. Previous reports have shown a significant correlation between levels of airborne endotoxin and (1-3)--D-glucan (4). So while we all would like to see a specific agent as the reason for effects found, the environment seldom provides this opportunity. From a practical point of view, however, endotoxin is useful as a marker for risk, and a reduction of these levels, particularly in occupational settings, will reduce the risk, whether this is related to endotoxin or some other covarying agent.

Ragnar Rylander

BioFact, Inc., Lerum, Sweden

FOOTNOTES

Conflict of Interest Statement: R.R. does not have a financial relationship with a commercial entity that has an interest in the subject of this manuscript.

REFERENCES

1. Thorne PS, Kulhánková, Yin M, Cohn R, Arbes SJ Jr, Zeldin DC. Endotoxin exposure is a risk factor for asthma: the National Survey of Endotoxin in United States Housing. Am J Respir Crit Care Med 2005;172:1371–1377.[Abstract/Free Full Text]
2. Rylander R. Endotoxin in the air: is it good for you or bad for you? Clin Pulmon Med (In press)
3. Rylander R. (13)--D-glucan in the environment: a risk assessment. In: Young S-H, Castranova V, editors. Toxicity of (1-3)--glucans. Boca Raton, FL: CRC Press; 2005. pp 53–64.
4. Rylander R, Beijer L. Microbial cell wall products in different fractions of house dust. Indoor Built Environ 2003;12:239–241.

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