The Immune Response

by Geneva Coats

THE IMMUNE SYSTEM

The body is continually subject to invasion by various bacteria, fungi, and viruses. Some bacteria even live in harmony with our body and are of benefit to us. Most of us have heard about the benefits of consuming "probiotics" in our diet, such as the active bacterial cultures in yogurt. These are the same strains of beneficial bacteria which are naturally present in our colon,  which  fight off the "bad" bacteria which can produce illness. These "good"  bacteria  produce Vitamin K, which is necessary for blood clotting. They also produce B vitamins, including Vitamin B12, which is essential to prevent anemia. If you are on a course of antibiotics the "good" probiotic bacteria is killed right along with the "bad" bacteria! It is beneficial in this situation to eat foods with probiotics (such as yogurt and kefir) to help restore the normal intestinal flora.

Sometimes micro-organisms can become "pathogenic" or disease-producing. The first line of defense against these foreign invaders is the skin, which provides a physical barrier to their entry. The skin normally contains many resident bacteria. Acidity in the stomach kills many bacteria which are ingested. The respiratory tract has long passages which are lined with mucus and cilia to help remove bacteria and prevent infecton. The cough reflex serves to keep harmful microbes out of our lungs.  However, sometimes pathogens are able to overwhelm our natural defenses and enter the body through the respiratory tract, GI tract, or a break in the skin.  Then, the body's immune system must become activated to eliminate the pathogens.

 The basic components of the immune system are the white blood cells. There are several different major types of white blood cells. Each type plays a unique role in the immune response. One major type of white blood cells  are lymphocytes. The lymphocytes are produced by the bone marrow and thymus gland, as well as by the spleen and lymph nodes.

If pathogens manage to travel past the first line of defense, through a cut in the skin or through mucus membranes, their next stop would be the lymph nodes (if they do not remain in the local area). The lymph nodes act as filters, with an internal honeycomb of connective tissue filled with lymphocytes that collect and destroy bacteria and viruses. When the body is fighting an infection, these lymphocytes multiply rapidly and produce a characteristic swelling of the lymph nodes. Clusters of lymph nodes are found in the underarms, groin, neck, chest, and abdomen.

There are two different  types of lymphocytes, known as "T cells" (thymus derived) and "B cells" (bone marrow derived). Both T and B cells produce a very important substance called interferon. Interferon is an antiviral and antitumor agent. There are several types of interferon. Interferon has been manufactured in labs and used in humans to treat viral hepatitis and leukemia.

A major role of the "T cells" is to directly attack foreign cells by seeking out, attacking, and destroying them. They engulf and literally "eat" the pathogens! T cells are directed by the thymus gland, so an immune booster will also encourage proper thymus gland functioning. (The problem in AIDS patients is a deficiency of a specific class of T cells, leaving the patient susceptible to certain bacterial and fungal infections, as well as tumors).  T cells, together with other white blood cells, travel to a localized site of infection. There they destroy the microbes, and can be noticed as pus in a wound. T cells also produce other factors which direct and assist in the immune response.

The other class of lymphocytes, the  B cells, produce antibodies in response to a specific foreign protein, or "antigen". These antibodies attach to the foreign viral or bacterial antigen and destroy it.

This is the premise of vaccination. A modified version of a disease organism is injected into the body. It is modified and weakened so that it will not produce disease. However, the presence of the foreign cells stimulates the B cells to produce antibodies against that specific disease organism.  The next time you come into contact with that particular pathogen, your body "remembers" it, and quickly produces antibodies to destroy it.  Clinical illness will not occur, or will be brief in duration.

 However, viral infection and/or recent vaccination with modified live-virus vaccines for  distemper, adenovirus, and parvo, have become recognized as contributers to immune-mediated disease. The current explosion of autoimmune problems seems to parallel the introduction of MLV vaccines in recent years. Autoimmune thyroid disease has become a very common canine condition. According to Dr. Jean Dodds, administering multiple vaccines frequently to the immature immune system of a stressed puppy may cause temporary or long-term immune system damage. Additionally, all animals in the household are exposed to live virus shed by those recently vaccinated with any modified live virus vaccine, and could become infected.  There is the risk of acquiring the actual illness from the vaccine if the immune system cannot mount an effective defense. These risks must be weighed against the benefits of protection from infectious disease when planning a vaccination protocol. Killed virus vaccines are safer but offer lower rates of effectiveness.

Interestingly, canine parvovirus, which first occurred in 1976, is theorized to be a mutation of the modified live virus vaccine for feline panleukopenia. Both viruses are nearly identical in structure. These diseases profoundly affect the immunity of their host by suppressing the bone marrow, which produces the blood cells.

Scientists believe that tumor cells occur on a daily basis in the body. Usually the body will recognize as abnormal and eliminate tumor cells through T cell activity and a direct attack on the abnormal cells. If the immune response is not strong enough, infection or tumors can become established.  Immune stimulants may be useful for these conditions.

Hyperactive cellular immune responses can produce autoimmune diseases and allergies, while hypoactive cell-mediated immunity causes immune supression. When immunity is supressed, the body is susceptible to infection and tumor formation.

IMMUNE DEFICIENCY; THE ROLE OF IMMUNE STIMULANTS AND ANTIOXIDANTS

Many dietary supplements have been found to support and stimulate the immune system, thereby helping to fight off invading pathogens, destroy abnormal tumor/cancer cells, and prevent disease.

Immune deficiency can happen when the body's normal defenses are suppressed. This immunosuppression can result from certain viruses, drugs, radiation, cancer, stress, trauma, or systemic infection. Immune-suppressant viruses of the retrovirus and parvovirus classes are known to cause bone marrow failure, immune-mediated blood diseases, blood cancers such as lymphoma and leukemia, organ failure, and autoimmune  diseases. In cases of immunosuppression (except those resulting from blood cancers), immune stimulants may be helpful in improving health.

Immune stimulants encourage the activity of these white blood cells (both B and T cells). Many vitamins, as well as some plant extracts, act as immune stimulants. These include garlic, high doses of zinc, selenium, vitamin A (including beta carotene), vitamin E and vitamin C. Several herbs stimulate immune function (echinacea, ginseng and astragalus are examples).

Zinc is an important mineral which helps delay the spread of cancer cells through the body.  Selenium and iodine are necessary for normal thyroid function and immune function. Other nutritional factors that play an important role in immune function are vitamin B6, and linoleic acid.

The nutrient glutathione is considered an immune-boosting substance. Glutathione is manufactured by the body, but its production is stimulated by sulfur-containing foods. Selenium is also necessary for glutatione production. Foods which encourage glutathione production are eggs, asparagus, broccoli, avocado, spinach, garlic and onions. Garlic and onion contain many tumor-inhibiting substances, but it is the selenium within these allium vegetables that gives them anti-oxidant properties. (Garlic and onions in large quantities also may cause anemia or low platelets in some dogs, more about that later).

Beta carotene, the nontoxic precursor to Vitamin A, deactivates free radicals. This is an example of what is referred to as "antioxidant" activity. Irritation of tissues by free radicals is thought to be one cause of tumor cell formation as well as aging of tissues. Antioxidants inactivate free radicals from the body, thereby reducing the risk of cancer and degenerative disease.

Carotenoid antioxidants are found in dark green and orange vegetables, and include lutein, lycopene, zeaxanthin, and canthxanthin. Bioflavanoid antioxidants (such as reservatrol, rutin, hesperidin, and quercitin) are present in dark blue and red fruits and berries. Vitamin E is also known to have strong antioxidant capabilities.


Studies have shown that vitamin C stimulates effector cells, which are a type of protective T cell. Vitamin C also protects effector cells from their free radical by-products.

Pantotheine, the coenzyme form of pantothenic acid (vitamin B5), also stimulates T cell activity. This substance is naturally found in all cells, and is supplemented in the form of calcium pantothenate.

Echinacea extract stimulates the formation of antibodies, inhibits hyaluronidase (an enzyme produced by many bacteria to gain access to the body's cells), and increases the production of interferon (a viral-fighting substance).

Astragalus, often packaged as the Chinese herb Qiang gan ruanjian tang, is known to stimulate the immune system. It activates T cells and helps to produce interferon.

The tropical plant known as mathake (Terminalia spp) is considered an immune enhancer.

Rosmarinic acid, derived primarily from the herb Rosemary, is sometimes used as a pet food preservative. It has antioxidant properties. Because of their potent antioxidant properties, Vitamins E and C are also used as short-term preservatives in some commercial dog foods.

White willow bark contains high concentration of salicylic acid, the precursor to aspirin, and the primary immune hormone in plants. In moderate doses, it triggers the immune response, has antibiotic properties, and reduces inflammation.

Reishi, and shiitake mushrooms enhance the immune system. The shiitake mushroom contains lentinan, an ingredient that has been shown to kill viruses, stimulate interferon, and stimulate T-cell activity to prevent tumors. 

Experiments in Japan reveal the immune-enhancing effects of chlorella, which also has antiviral and antitumor effects and greatly stimulates the production of interferon.

Antioxidants are being identified every day, and there are many other immune stimulants.

TOO MUCH OF A GOOD THING....AUTOIMMUNE PROBLEMS AND ALLERGIES

The term "Autoimmunity" literally means "immunity against self". The body's defenses become unable to differentiate between "self"  and "foreign". The immune system then attacks and destroys  the body's own tissues or organs.  These autoimmune problems can affect a wide variety of tissues, including the thyroid gland, adrenal gland, and the pancreas, creating a diabetic condition. They can even effect the joints, causing arthritis, and the skin, hair follicles and connective tissues, as well as the red blood cells and platelets. The scientific terms for these problems are autoimmune thyroiditis, Addison's disease, diabetes, idiopathic thrombocytopenic purpura (ITP), Immune mediated hemolytic anemia, rheumatoid arthritis, pemphigus, lupus, and dermatomyositis. These conditions have a definite adverse effect on the quality of life for our dogs, causing them pain and suffering.

In humans the ability to develop an autoimmune disease is determined by a dominant genetic trait that is very common (20 percent of the population) that may present in families as different autoimmune diseases within the same family. The genetic predisposition alone does not cause the development of autoimmune diseases. It seems that other factors need to be present as well in order to initiate the disease process. Numerous viruses, bacteria, chemicals, toxins, and drugs have been implicated as triggers in susceptible individuals. The four main causes of autoimmune disease are felt to be:

1. Genetic predisposition

2. Hormonal influences, especially of sex hormones

3. Infections, especially of viruses

4. Stress 

 For dogs with autoimmune problems, ie. an over-stimulated immune system, the immune system needs to calm and regain normal control functions; it does NOT need further stimulation. For these dogs, immune stimulants should best be avoided. 

The high sulfur content of garlic and onions may be responsible for stimulating an autoimmune hemolytic anemia, in which the body destroys its own blood cells. Sometimes platelets in the blood are destroyed by this autoimmune reaction. Platelets are a key component in blood clotting. When they are destroyed, the dog experiences a tendency to bleed easily.

 If you are using "green" supplements with spiruina and chlorella, bear in mind the possible immune stimulant effect on a dog with an autoimmune problem. Any of the previously mentioned immune-stimulants, vitamins, and antioxidants  should be used with caution, if at all, for the dog with an autoimmune disease.

For the dog with an autoimmune problem, or with blood cancers such as lymphoma or leukemia, vaccinations should be administered conservatively, if at all.

Allergies are another type of hyperactivity of the immune system, with similar treatment as the autoimmune disorders. Steroids and other anti-inflammatory drugs are commonly employed in these situations.

CORTICOSTEROIDS (such as Prednisone, Cortisone, Decadron and Solu-Medrol) reduce inflammation and suppress the immune response. These drugs are useful for inflammatory conditions such as arthritis, asthma, colitis, allergies, and autoimmune hepatitis. 

Steroids are naturally produced by the adrenal glands in response to stress. However, they can have a number of serious side effects on the body. Osteoporosis is a particular concern because the drug causes loss of calcium from bone. Extra calcium and vitamin C and D in the diet are generally recommended. Steroids such as prednisone tend to raise blood sugar and produce a diabetic condition. Steroid use also renders the patient susceptible to infection, due to the supression of the immune response. Long term use of steroids promotes stress ulcer formation.

However, steroid drugs have a very important role in medicine. They are life-saving in treating autoimmune hepatitis. For acute inflammatory conditions such as ulcerative colitis and Crohn's disease, they are able to bring symptoms under control very quickly. Steroids are often necessary to control acute allergic inflammatory conditions such as asthma or dermatitis.
Whenever possible, the patient is tapered off the drug fairly quickly to avoid long-term use. The lowest effective dose is generally used. Steroid use should NEVER be abruptly discontinued, but tapered off under your vet's supervision.

If you keep in mind that autoimmune diseases are familial in nature, it can assist you in making breeding decisions. The tendency to autoimmunity, like so many other health problems, is thought to be hereditary.

Copyright 2006. This article may not be reproduced or distributed in any form without express written consent of the author.