The Immune System

There are some elements of the immune system that we may not think of as such. For example, the skin and the lining of the gut, but the function of both is protective, which is what the immune system as a whole is designed for. The skin, for example, is waterproof and keeps many organisms from penetrating the body, as well as holding the body in place, and the linings of the gut, the respiratory organs, and so on, can be thought of as another skin.

Another component of the immune system is the lymphatic system, which is part of the drainage system of the body. The lymph nodes are glands situated on the lymphatic vessels (which are the means by which the lymph [a fluid similar to blood plasma, which nourishes the tissues and returns waste products from them back into the bloodstream] is carried through the body. This could be likened to a canal system between various towns and villages in an area). The lymph nodes act as filters and have an important role in the body's defence system by producing lymphocytes. There are some areas of the body which do not have a blood supply (for example, the cornea of the eye, and cartilage) and in them the lymph is their only means of gaining nourishment.

The lymph nodes are the part of the immune system most readily seen, as the superficial ones (those closest to the surface of the body such as in the throat area and behind the ears) can be felt and, when greatly enlarged, can be seen. When a disease condition is in the area of the body local to the lymph nodes, the nodes swell up as they produce lymphocytes in order to help fight off a disease. There are other lymph nodes deeper within the body that cannot be felt.

Lymphocytes in mammals are actually of two main classes: one derived from the thymus, and called T-cells; and one derived from bone marrow and called B-cells. T-cells act directly on foreign cells, while B-cells divide rapidly to form plasma cells which secrete antibodies.

Antibodies are proteins produced by lymphocytes, and lymphocytes are cells which are a sub-population of the white blood cells. All the white cells are involved in the immune system and, when there is a disease present, the number of white cells will increase in order to fight the disease, so raised levels of white cells found in a blood test are evidence of the presence of disease.

Antibodies belong to a group of proteins called Immunoglobulins and are protein molecules of complex structure. In the immune response, antibody and antigen molecules combine to form a complex, and these complexes are removed from the body by the reticulo-endothelial system. Antibodies are not always protective. Some antibodies join mast cells (a type of connective tissue cell) and eosinophils (white cells found in the blood stream and pituitary and pineal glands) and, when exposure to the specific antigen takes place, the result is the release of histamine, as occurs in allergic responses. The reticulo-endothelial system depends upon special cells present in the liver, spleen, lymph nodes, and bone marrow. As well as removing antigens from the body, they also remove red cells from the blood.

The immune response is the body's reaction to the presence of foreign substances (such as are present in bacteria, viruses, and other parasites but which are dissimilar to any occurring naturally in the body) These foreign substances act as antigens and stimulate the production of antibodies. Lymphocytes attack cells containing antigens and thus play an important part in the immune response.

Other of the white cells are phagocytes, of which the most active is the monocyte. Phagocytosis is the process by which the attacks of bacteria upon the body are repelled and the bacteria destroyed through the activity of these white blood cells. Bacteria coated with antibodies are phagocytosed more efficiently.

Other components of the immune system are enzymes and various types of secretion that help prevent disease. Our skins are covered with bacteria even when they appear clean. These bugs co-exist quite happily and stop other, possibly damaging, organisms taking over. These are particularly important in the gut.

An antibody combines to a microbe and can prevent by its presence the organism being able to activate. Where an antibody has bound to a cell, other proteins attack the organism. Blood can be taken from a dog, without causing any harm to the animal, and the serum tested for the presence of antibodies. It can be found, firstly, whether the dog is responding to a disease organism and how well it is reacting: e.g. it can be found if there are antibodies present which combine with the distemper virus. Or it can be found if the dog's immune system is reacting inappropriately, for example to foods or even its own tissue or other parts of itself, as in auto-immune disorders.

In eosinophilic disorders , which produce symptoms of allergic reaction, the allergy is really only a side effect of what is basically a reaction of the eosinophils to invasion by parasites.

There are other components of the immune system, such as the spleen, and the adrenal glands. The adrenals are tiny and perch next to the head of each kidney. They are part of the endocrine system, which is a system of glands which secrete substances which have specific effects on other organs and parts of the body.

For all their small size, the adrenals have a major workload. Part of the gland - the inner cortical layer - produces the sex hormones oestrogen and androgen - and another part - the medulla - produces the hormone adrenalin - the flight or fight hormone. The middle layer of the cortex produces another hormone, cortisol, which regulates the activity of the lymphocytes. The cortisol is in turn regulated by another hormone, adrenocorticotropin [ACTH], produced by the pituitary gland. ACTH stimulates the adrenal gland into producing more cortisol when levels are too low and stops production when there's too much.

According to vet Alfred J. Plechner in his book Pet Allergies: Remedies for an Epidemic, this middle part of the adrenal cortex is often defective and fails to produce enough cortisol and this leads to major problems with the functioning of the immune system, especially producing allergic reactions and auto-immune disorders. A lack of cortisol production can also lead to symptoms of hypothyroid, because cortisol is required for the uptake of the thyroid hormone. In this case, there are adequate (or even too large) amounts of thyroid hormone circulating in the blood stream, but the cells are unable to utilise it properly. However, auto-immune thyroiditis is the commonest cause of hypothyroid in dogs.

Vaccination is a manipulation of antibodies. The rationale behind it is that virus inactivated in some way prevents it giving the disease but still stimulates the immune response. The immunological memory induced by the vaccine does not stop the disease but brings the immune system into play very quickly. The immune memory has to be stimulated in order to mature and only by exposure to the disease can immunity be effected. This occurs when exposed to the disease itself, or when given a vaccine.

The immune system itself (rather than the immune response, which is what is stimulated by vaccines) can be strengthened by a good diet, orthomolecular therapy, herbs, homeopathy, and various other therapies such as acupuncture and BodyTalk (or Animal Links). See the Nutrition and Alternative Therapies pages for further information. One possible cause of immune system problems is geopathic stress. Click here for more on this subject.

There are various ways in which the immune system can malfunction. These include immune deficiency, allergic reactions and sensitivities (which are brought about by the immune system reacting inappropriately to what should be harmless substances), and auto-immune diseases.

Detection of immune deficiency:

  1. Unexplained illness or death of more than one puppy in a litter. Especially if subsequent litters of the same parentage also suffer.
  2. Illness caused by organisms that are normally commensals (ones which normally live on us without causing problems) or unexpectedly caused by an organism of low pathogenicity.
  3. Severe or recurrent illnesses that are unusually difficult to control. With treatment, what we are doing is adding that treatment to the body's normal healing mechanism.
  4. Failure to respond to vaccination. However, it is difficult to prove the animal has not been in contact with the disease before vaccination.
  5. Disease resulting from the use of attenuated live vaccine. With parvo there is another way in which vaccine can fail; we rely on Nature to give antibodies from the mother to the puppy. In the first few weeks of life the puppy can rely on this to prevent illness. The other side of the system is that the puppy cannot respond to vaccination if the maternal antibodies fight with the vaccine. Parvo antibodies seem to affect vaccination far more than any others. The circulating antibodies from the mother are slowly eliminated by the puppy as they are foreign bodies.

Virus rhinitis in the wolfhound is considered to be an immune deficiency disorder. In such a disorder the basic problem is not the viral infection but the underlying immunodeficiency. Some veterinarians consider canine parvovirus to be an immunodeficiency disorder, and there is a possibility that some cases of dilated cardiomyopathy might be also. There can be an acquired deficiency syndrome, which can follow another disease or non-infectious causes such as tumours or leukaemia. Viral and bacterial disease can cause immuno-deficiency diseases as well as being the result of them. Aspergillosis is a fungus which reduces immune response, and there can be inherited disorders which reduce the efficiency of the immune system, for example primary ciliary dyskinesia. It is also possible that diet and nutritional deficiencies or imbalances can weaken the immune system.

Detection of adrenal insufficiency

According to Alfred J. Plechner in Pet Allergies, a simple blood test is all that is necessary, two samples being taken - the first between 8 and 11 am and the second two hours later. Immediately after the first blood sample is taken, the dog is given an IM injection of pituitary ACTH. No food should be given during the two hour wait between the taking of blood samples. Full details of how this procedure is carried out and how to read the test results are given in the book.

Dr, Plechner states that the disorders due to adrenal insufficiency include chronic skin problems (including flea allergy, food allergies, and inhalant and contact allergies); digestive disorders; and behavioural instability, among others.

Auto-immune disorders

This is where the immune system fails to recognise "self" and attacks some part/s of the body as though it were a foreign substance. The body's recognition of self starts in the womb and at and just after birth. At this time the immune system is unable to mount a response, so when it encounters body components it has to accept them as part of itself and should continue to do so. However, some parts are "hidden" at this stage of development; that is, not yet present or incompletely so - such as spermatazoa and myelin - and so these components can be seen as antigens. However, it is considered probable that there are a number of factors that can lead to the immune system reacting to self.

These include nutritional influences such as imbalances or deficiencies of trace elements, vitamins, or other nutrients; chemical preservatives or other toxins in food; chemical or drug residues; fungii; viral infections; frequent or recent use of Modified Live Virus vaccines, and/or multivalent (combination) vaccines; stress whether environmental, emotional or physiological; underlying disease; adverse drug reactions. Other ways in which vaccines could lead to auto-immune disorders is through the chemicals they contain and also through the animal proteins they contain such as foetal calf tissue, which is similar enough to a dog's tissue to cause the immune system to react against its own body or some part(s) of it.

Some common autoimmune disorders are autoimmune thyroiditis (a cause of hypothyroid) (click for more details on thyroid disorders), autoimmune haemolytic anaemia, autoimmune thrombocytopaenia. It is possible that dilated cardiomyopathy, the heart condition most common in wolfhounds, could be an autoimmune disease in which the immune system attacks the heart muscle. (click for more details on heart disease)  The Canine Immune System and Disease Resistance By W. Jean Dodds, DVM
merck veterinary manual The Merck Manual for Pet Health page on Immune System Responses in Dogs The Pet Place page on Structure and Function of the Immune System in Dogs Pamela A. Davol's Wing-N-Wave Labradors website page on the canine immune system, listing many articles on the subject.

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Updated 8/11/2015