Dirty Environments Vs. Immunocompetence

When a child is brought up in a pathogen-saturated environment, the immune system is constantly working. As such, the immune system “adapts” to the environment and no longer is irritated by minor irritants such as pollen and even minor pathogens that do not pose a large threat to the body.

Duke University’s Dr. William Parker ran a study to show that rats living in the sewers were, indeed, in better health than their clean cousins living in laboratories.

His study showed that when the same (minor) stimulus is applied to the immune systems of two rats, one brought up in the sewers and the other in a clean lab, the immune system of the rat brought up in a clean environment responded with a very aggressive, over-stimulated defence, while the immune system of the first rat (brought in an unclean environment) did nothing. Dr. Parker hypothesizes that when the immune system of a rat, and theoretically that of a human, is not stimulated as much during childhood, it becomes hyper-stimulated by what should be a mild stimulus, creating allergies, asthma, and other autoimmune diseases.

Dr. Parker also noted that the rats that had been brought up in a dirty environment had four times the immunoglobulins, or antibodies, that the lab rats had in their blood, but were not actually sick. The reason for the higher levels of immunoglobulins has not yet been discovered.

Graham Rook, a professor at the Centre for Infectious Diseases and International Health at the Royal Free and University Medical School in London, UK, has an extension to offer to this hypothesis; that there are harmless microorganisms that once helped prime our immune systems, but are now missing from our society.

“The 'old friends', as we call them, are all either things that really do us no harm, or things where the immune system is forced to give in and avoid a fight because it's just a waste of time,” explained Rook. Due to this, the immune system would have to learn to tolerate foreign matter, and hence practice massive immunoregulation.

However, if an environment is too pathogen-saturated, then the child may not survive against pathogen attacks. Hence, a balance between clean and dirty environments must be found.