Clean Environments Vs. Immunocompetence

In a clean environment, the body theoretically has less to do to protect itself from infection, and hence starts to pick at the little details, causing hypersensitivity. The immune system is based on the concept of recognizing self as opposed to non-self, but in hypersensitivity, the body does not recognize parts of itself to be itself, and attacks it.

According to Dr. Parker’s and Graham Rook’s research and hypotheses, this could be because the immune system is not challenged enough by pathogens, and starts worrying about little details. As well, the immune system may have at one point be primed by microorganisms that Rook calls “old friends”, which are no longer present in our bodies owing to the new standards of society.

Rook uses the example of helminths in order to demonstrate his theory. According to him, once a worm the size of a helminth invaded the body, the immune system would have been so overwhelmed by it that it would simply have to tolerate the attack through immunoregulation. Rook believes that the immune system “taught” itself in such a way, and that it could practice immunoregulation thus, and hence ignore minor problems that it might encounter instead of going through a complete response.

Statistics show that in Western civilization, the rates for allergies and autoimmune diseases are significantly higher than those in third world countries. They also show that these rates have been increasing with our cleaner standards.

If a child is allowed to grow up in an environment that has very few pathogens, then they are far more likely to develop some type of hypersensitivity than are children brought up in an environment that has a high concentration of pathogens. There are four types of hypersensitivity:

Type I: Immediate (Allergy)

This is an allergic reaction provoked by reexposure to a specific antigen. This exposure may be through inhalation, injection, ingestion, or direct contact. An inflammatory response is provoked, whether local or systemic.

Examples: Allergic Asthma, Anaphylaxis, Allergic Rhinitis.

Type II: Antibody-Dependant

The body attacks antigens found on the person’s own cell membranes. These antigens may be part of the body, or absorbed from foreign molecules. This causes acute inflammation and the cells are destroyed. In another form of type II hypersensitivity, the cells displaying the antigens are tagged by antibodies and destroyed by Killer T-cells (Cytotoxic T-Cells) or macrophages, which recognize the tag.

Examples: Erythroblastosis Fetalis, Rheumatic Fever, Farmer’s Lung

Type III: Immune Complex

Soluble aggregations of IgG and other antibodies are formed in the bloodstream, and are released into the skin, kidney, and joints, where they may elicit an immune response.

Eg: Rheumatoid Arthritis, Immune Complex Glomerulonephritis

Type IV: Cell-Mediated/Delayed

This is cell-mediated immunity, involving only T-cells and no antibodies. A T-cell response is stimulated by the body’s own cells.

Examples: Transplant rejections, Contact Dermatitis.

It is important, however, to note that a lack of exposure to pathogens will cause less chance for death due to an ordinary disease.