The Immune System
From the book:
Immunology, simply stated, is the study of the immune system. This vital system usually is rarely noticed by most people. After all, how many people spend a lot of time reflecting on their good health? Yet, no one would live very long without a healthy immune system. Why? The body is continually bombarded with potential disease causing agents such as bacteria, viruses, or the occasional mutated cell, like cancer.
That sounds ominous, and it would be were it not for the immune system. Fortunately, when this internal protector is working properly, most threats are nipped in the bud before infection or other problems become Sufficiently serious to adversely affect body systems. (The reason why AIDS is such a serious condition is that the HIV virus destroys the immune system, leaving the infected person exposed to diseases that the body would normally have easily shaken off.) The soldiers of the immune system are cells known as white blood cells, one of which is a lymphocyte. Lymphocytes, are found everywhere in the body because, they circulate freely throughout the body alongside red blood cells (which supply oxygen to the body).
There are three principal types of lymphocytes. Simply put (the actual workings of these cells is quite complex), here is how they function:
B-lymphocytes: About 10-20% of lymphocytes, known as B-cells, are stimulated by certain microorganisms. When this happens, each stimulated B-cell divides and makes thousands of clones of itself. These clones then enlarge, making thousands of what are known as plasma cells. These plasma cells, in turn, secrete substances known as antibodies into the blood system, which attack the invader and destroy it. The body has hundreds of thousands of different B-cells. Amazingly, each has the potential to make a specific antibody.
T lymphocytes: Approximately 70-80% of white blood cells are T lymphocytes. These cells stimulate B-cells to do their work, and also kill invaders by attaching directly to the unwelcome organisms (rather than creating antibodies) or abnormal cells. Once T cells attach to the organism, the cells release chemicals which destroys the invader.
NK cells: About 10-15% of lymphocytes are natural killer cells. These cells serve two important functions; a) they detect and destroy cells infected by viruses preventing them from becoming "virus producing machinery', and b) they detect and destroy small cancer cells before the cancer cells consolidate into a tumor.
Some lymphocytes serve as memory banks for the rest of the immune System. Unlike most lymphocytes, these lymphocytes live for many years. These cells do not participate directly in killing the invader but rather serve to stimulate the proper response in other cells.
If the lymphocyte system were the only working part of the immune system, it would be an extraordinarily complex and wondrous system. But that is just the beginning. The next important group of molecules in the immunological equation are the human leukocyte antigens (HLA). The HLA are found on the surfaces of most cells, including organ cells, and were discovered in connection with transplantation research. To make a long story short, we now know that HLA are important in immunological recognition of any abnormal presence in the body, including cancer cells, microorganisms and foreign substances.
The genes that produces HLA are named, Class I, Class II, and Class III. Gene classes I and II encode the HLA molecules with immune recognition, while the remaining class is involved with the inflammatory process. (The inflammatory process causes blood to rush to the sight of injury or disease resulting in heat, swelling, and pain.) Not surprisingly, there are also many subcategories of HLA types, the details of which can wait for another day and another book. However, it is important to note that each person inherits one half of their HLA types and subtypes from each parent.
HLA are essential to the body's recognition of substances which are "self" from those which are "foreign." Thus, when a virus attaches itself to a cell, HLA and the T-cells are able to recognize that something is amiss, which in turn activates the proper immune response required to destroy the invader. (This is the problem that occurs with transplants. The immune system sees the new organ as a foreigner and acts to destroy it. Thus, immunosuppressant therapy is required to allow the transplant to "take.")
All of this has great relevance to pregnancy. We start from the basic premise that no two humans are genetically identical except for identical twins. (Identical twins are formed when the same sperm fertilizes one egg. Then, after the first cell division, each of the two cells develops independently thereafter.) Thus, when a woman becomes pregnant, the fetus, like a transplanted organ, can be identified as foreign, since only half of the developing life is identical to the mother's biology. That, of course, would cause big trouble, were defenses not available to prevent the fetus from being destroyed. Happily, in a normal pregnancy, the immune system is prevented from attacking the developing fetus as if it were an unwanted foreign object via B-lymphocytes and antibodies they produce. In addition these antibodies participate in the growth and development of the placenta.
One of the vital areas of the placenta is the layer known by the tongue-twisting name of syncytiotrophoblasts. (We'll call them syncoblasts, for short.) Syncoblasts are made up of giant cells which regulate the flow of nutrients between mother and fetus. They also act as a vital barrier between the maternal immune system and the fetal immune system, both of which would otherwise react to the other as foreign to self, especially since much of the early fetal HLA response is inherited from the father! Clearly, trouble could brew in such an atmosphere, were not the immune systems of both mother and fetus kept from reacting to each other. Meanwhile, the mother's immune system protects the placenta from attack by microorganisms.
Autoimmune Disease and Pregnancy
Autoimmune disease means that one's immune system attacks one's own tissue. Such diseases may or may not affect a pregnancy and the chances to carry fully to term. These diseases could affect a proposed or current pregnancy and should definitely be discussed with your doctor. Here is a general overview of the autoimmune-related conditions:
Rheumatoid Arthritis: Rheumatoid arthritis (RA) is a painful, chronic disease, that generally affects people between the ages of 20-60, including women of child-bearing age. (Two to three times more sufferers are women than men.) People with rheumatoid arthritis (arthritis is joint inflammation) will suffer painful swelling in the joints of the fingers, wrists, toes, and/or any other joint in the body. In severe cases, the joint areas of the body may become deformed, or other body systems affected.
RA is an autoimmune disease, in which the immune system has been stimulated into attacking its own body. In other words, the system does not recognize "self" as self but rather, acts as if it is "other." Treatment requires drugs to be taken to reduce this response.
Happily, rheumatoid arthritis has little effect on a pregnancy. Indeed, a pregnant woman with rheumatoid arthritis may notice a small improvement in her condition. In addition, many of the medications taken to reduce the symptoms of the disease, has no significant impact on the fetus.
Systemic Lupus Erythematosus: Lupus is another autoimmune disorder in which the body's immune system attacks the connective tissues, causing illness and inflammation. Lupus symptoms, which ebb and flow, include a recurring butterfly-shaped rash, hair loss, sensitivity to light, malaise, fatigue, fever, loss of appetite, nausea, joint pain, and weight loss. Severe cases can lead to kidney failure, pleurisy (an inflammation of the lining of the lungs), arthritis, and inflammation of the membrane surrounding the heart. About 9 times as many women as men suffer from lupus--significantly, during child-bearing years -- with some estimates of female cases being as high as one in every 250. Lupus may be a cause of increased uterine infection. Worse, in the context of this book, women with lupus experience an increased incidence of a condition called preeclampsia. Preeclampsia is a condition that can develop in the second half of pregnancy, inducing high blood pressure, fluid retention and protein in the urine, headache, nausea, vomiting and abdominal pain. If untreated, the condition can lead to eclampsia, which can cause seizures, miscarriage, and/or even death.
Women with lupus may have difficult pregnancies, experience miscarriage, and premature birth, and have babies with a low birth weight, or are stillborn. Pregnancy may also accentuate the seriousness of lupus. Thus, any woman who has been diagnosed with the disease should discuss the matter completely with her doctors before becoming pregnant.
Myasthenia gravis (MG): MG is a disease which causes a weakening of the muscles and fatigue. The condition is most often evidenced by drooping eyelids, a blank facial expression, hesitant speech, and difficulty eating. This disorder is caused when the immune system, for reasons that are not understood, attacks the part of the muscle that is responsible for receiving signals from the nerves. Eventually, this causes muscles to not respond to nerve stimuli. The condition, which thankfully is rare, generally attacks women of child bearing age and men between the age of 50 and 70. Most people are able to lead fairly normal lives with MG, although a small number of victims are eventually killed by the condition.
The good news is that MG generally does not seriously impact a pregnancy. Autoimmune response to pregnancy is a significant cause of recurrent miscarriage. Indeed, if you have a history of miscarrying, the chances are 50% that your own immune system is the primary cause.
This is a serious matter. If immune system-caused miscarriages go untreated, after three miscarriages, the chance of bringing a pregnancy successfully to term, thereafter are only 30%. After 4 miscarriages, the chances of a successful pregnancy are reduced to 25% and after 5 miscarriages, the chances of a successful birth plummet to just 5%.
The medical world has been slow to recognize that this condition can be treated. Treatment of miscarriage is still considered controversial, and "experimental." In the real world, this means that health insurance will often not pay for the care, which can be quite expensive, despite the quite remarkable fact that properly treated, a woman who has suffered autoimmune-caused recurrent miscarriage can be Successfully treated between 75-85% of the time. We now turn to Some Specifics.