February 13, 2007

By Dr. Rodney R. Dietert, Cornell University, and Janice M Dietert

Developmental immunotoxicity (DIT), best defined as an exposure to environmental toxins during pregnancy and early childhood, is increasingly being implicated by researchers as a major cause of life long illness.

To understand how this is possible, the developing immune system has been carefully studied. For one thing, the pregnant mother’s immune system must be Th1 depressed as if she were receiving immunosuppressant drugs after an organ transplant. Otherwise, her body would immunologically-reject the fetus and she would miscarry. Meanwhile, the fetus goes through gestation with an underdeveloped immune system particularly lacking the capacity to attack the mother’s cells for the very same reason. However, during the last trimester the baby’s immune system develops rapidly but only for those immune system components that would not jeopardize the pregnancy. And this is where the trouble begins. A late fetal immune system, if not further matured and better balanced after birth, is a significant health problem for the child and later-life adult. Immune cells are created for Th1 function (attacking viruses and cancer cells) and Th2 function (attacking parasites). Some are busy learning to tell the difference between self and non-self. Maturing cells have to leave the thymus and travel throughout the body, a process known as seeding. All of this must happen efficiently and be in place in the newborn for the child to have adequate protection against disease. Early-life immunotoxicants prevent this.

Originally in the era of AIDS, an immunotoxic environmental agent was thought of as a substance that would destroy most of the immune system and usually kill a fetus following in utero exposure. However, few toxicants actually do this. In fact, better technology has allowed researchers to see how the immune system develops and works and how most toxicants produce far more subtle, yet health challenging changes.

What researchers have found is that a majority of toxicants, such as heavy metal and PCBs, at real life exposure levels would not kill the fetus outright. Instead, many toxicants at low levels make it nearly impossible for the Th1 cells to develop. This means that the individual will have a fetal-like immune system balance for life. Other cells designed to tell self from non-self don’t learn the difference due to damage from toxins. In later life, this subtle immune change often results in autoimmunity. And cells that would ordinarily create inflammation as part of a wound/illness healing pattern now respond inappropriately creating hyperinflammation with problematic neurological and endocrine damage as a result.

With new research in the past decade, DIT is no longer seen as a path toward fetal toxic death but instead as a route toward chronic, life-long illness. DIT has been associated with targeted immune suppression, misdirected immune responses resulting in asthma, allergy and autoimmunity, as well as other exposure-related diseases involving the neurological and endocrine systems.

So far it appears that the following clearly result in DIT:

- certain herbicides, pesticides and biocides

- maternal alcohol consumption, cigarette smoking, and under nutrition

- second hand tobacco smoke

- certain chemicals (PAHs, PCBs, TCDD, DES)

- certain fungal toxins (alflatoxin, ochratoxin and T-2 toxin)

- xenoestrogens (DES and genistein [from soy])

- maternal infections and stress

- diesel exhaust

- heavy metals (lead, cadmium, mercury, arsenic, and manganese)

- certain medications (cyclosporin-A, antibiotics and diazepam)

- certain drugs of abuse

- C-section delivery

- preeclamsia

- some allergen exposures

There are also critical windows during the last trimester when these toxins present the greatest risk. An exposure to a potential allergen at the same time or soon after exposure to a toxin usually means that when the baby is exposed to that allergen again after birth, its body will more likely have an allergic response because the toxin exposure during pregnancy prevented its immune system from developing correctly. Thus the prenatal exposure to the toxin and the allergen molds later life immune response capabilities. Or toxin load from pregnancy, such as PCBs, may make it nearly impossible for the child’s immune system to adequately respond to vaccinations as has been seen in children from the Faroe Islands. Their immune systems are so damaged they cannot create the appropriate immune response when given a vaccine.

What we are seeing worldwide as a result of DIT is increased incidence of asthma, allergies, autoimmune disorders, CFS, infectious diseases, cancer, neurodegenerative diseases, cerebral palsy, atherosclerosis, hypertension and male sterility. Most of these illnesses are chronic, life long and costly both to the person and to society requiring a heavy investment in health care while lowering quality of life and productivity.

Even more challenging to researchers than discovering the costs of DIT is the issue of reversing or ameliorating the affects of toxins once the damage has been done. A mother could conceivably allow her baby exposure to a barnyard environment full of bacteria and potential animal allergens. The exposure to the environmental stimulants at that age on a farm would actually challenge the immune system (if done early enough) and prompt the Th1 side of the immune system to strengthen. Maternal supplement intake is also advised, particularly fish oil, as this can help reduce the likelihood of the child developing allergies.

Additionally, there are a few herbs that have shown promise for improving immune function. The caution when considering herbals to enhance the immune system is that, in a healthy person with a mature and well-balanced immune system, using the herbals might cause the immune system to swing too far to the Th1 side causing its own set of problems. However, in someone with an imbalanced "fetal-type" immune system, some herbals show promise in helping to enhance immune function on the Th1 side. They are:

- Astragalus

- Wild Yam

- Echinacea

- Reishi mushroom

- Maitake mushroom

- Shiitake mushroom

- Nigella sativa

- Panax ginseng

- Sang Hwang mushroom

- Sophora root

- Fenugreek

However, since each of these herbal medicinals affects the immune system differently, self dosing isn’t suggested. A good herbalist can help direct individuals in the use and combination of these herbs if so desired. The good news, though, is that scientists are beginning to give them a close look and are discovering how they actually work to enhance the immune system. As more is learned about them, methods to improve immune function in those challenged through DIT exposure may become available.

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