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Complement deficiencies


Related Terms
  • Antibiotics, antifungals, antibiotics, antifungals, antimicrobials, antivirals, autoimmune disease, autoimmune disorder, bacteria, bacterial infection, complement, complement proteins, complement system, immune, immune defense system, immune reaction, immune response, immune system, immunocompromised, immunodeficiency, immunosuppressants, infection, meningitis, pneumonia, recurrent infections, viral infection, virus, weakened immune system, white blood cells.

  • Complement deficiencies are disorders that occur when the body has low or nonexistent levels of specific proteins needed for proper immune function. Healthy immune function is important to protect the body from disease and infections. These proteins, which are part of the complement system, help destroy harmful invaders, such as bacteria and viruses, that enter the body.
  • The complement system is a group of more than 20 different proteins involved in the immune response. The complement proteins can destroy invading substances in many ways. For instance, the proteins can kill bacteria directly by poking holes in them. The proteins can also kill foreign substances that are attached to other proteins called antibodies. In addition, the complement proteins can bind to foreign substances, which triggers white blood cells to engulf and destroy the invaders.
  • Symptoms of complement deficiencies vary depending on the specific protein involved and severity of the deficiency. Patients with complement deficiencies are often vulnerable to frequent infections, especially pneumonia or meningitis (infection that causes inflammation of the membrane that surrounds the brain and spinal cord). Also, an estimated 90% of patients with complement deficiencies also develop autoimmune disorders, such as lupus. Autoimmune disorders occur when the immune system launches an attack against body cells because they are mistaken for harmful invaders.
  • Some patients are born with complement deficiencies. Researchers estimate that three out of 10,000 people inherit the disorder worldwide. Others may develop complement deficiencies as a result of other medical conditions, such as liver disease.
  • There is currently no cure for inherited complement deficiencies. Instead, patients receive medications called antimicrobials for infections and/or drugs called immunosuppressants for autoimmune disorders. If the complement deficiency develops as a result of another medical condition, such as liver disease, the disorder will be cured once the underlying cause is treated.
  • The average life expectancy for patients with complement deficiencies varies considerably. Some patients may experience no signs of the disease and live normal, healthy lives. Others may experience severe infections that can lead to death. Autoimmune disorders may lead to organ failure if they are not properly managed with immunosuppressant drugs.

Author information
  • This information has been edited and peer-reviewed by contributors to the Natural Standard Research Collaboration (

  1. Cook HT, Botto M. Mechanisms of Disease: the complement system and the pathogenesis of systemic lupus erythematosus. Nat Clin Pract Rheumatol. 2006 Jun;2(6):330-7. .
  2. Farhoudi A, Bazargan N, Pourpak Z, et al. Two related cases of primary complement deficiencies. Iran J Allergy Asthma Immunol. 2003 Jun;2(2):69-74. .
  3. Immune Deficiency Foundation. .
  4. Lewis MJ, Botto M. Complement deficiencies in humans and animals: links to autoimmunity. Autoimmunity. 2006 Aug;39(5):367-78. .
  5. National Institute of Allergy and Infectious Diseases. .
  6. National Institute of Child Health & Human Development. Primary Immunodeficiency. .
  7. Natural Standard: The Authority on Integrative Medicine. .

  • Genetic: Complement deficiencies can be inherited as an autosomal recessive or X-linked trait.
  • If the disorder is autosomal recessive, the patient must inherit one mutated (abnormal) gene from each parent in order to develop the disorder. Individuals who only have one mutated gene and do not experience symptoms are called carriers. Although carriers do not have the disorder, they may pass the mutated gene on to their children. Carriers have a 50% chance of passing the abnormal gene to each of their children. Both parents must either be carriers or have the disorder in order for their children to develop the disorder. If both parents are carriers of the gene, there is a 25% chance that each of their children will inherit the disease and a 50% chance that each of their children will be a carrier.
  • If the disorder is X-linked recessive, it will affect males almost exclusively because, unlike females, males have only one X chromosome. If a male inherits the mutated gene, he will develop the disease because he has only one X chromosome. Females, on the other hand, have two X chromosomes. Therefore, females only develop the disorder if they inherit two mutated X chromosomes. If the female inherits one mutated gene, she is a carrier for the disease, and there is a 50% chance she will pass the mutated gene to each of her children. Carriers do not experience symptoms of the disease.
  • Other medical conditions: Medical conditions that cause protein loss, such as liver disease, can lead to complement deficiencies. The liver is responsible for producing complement proteins. When it is damaged, it is unable to produce normal amounts of proteins.

  • General: Symptoms of complement deficiencies vary depending on the specific protein involved and the severity of the deficiency. Some patients may experience no symptoms and live normal, healthy lives, while others may experience frequent infections and/or develop autoimmune disorders.
  • Infections: Some patients with complement deficiencies will experience frequent infections. Patients should consult their healthcare providers if they experience general symptoms of infections, including fever, sore throat, or enlarged lymph nodes.
  • The most common infections associated with complement deficiencies are pneumonia and meningitis. Pneumonia is an infection of the lungs that may cause symptoms, such as shortness of breath, fever, nonproductive cough, chest discomfort, weight loss, chills, rapid breathing, fast heart rate, and mild crackles (bubbling, or rattling sounds that occur when air moves through fluid-filled airways). Meningitis is an infection of the membranes that surround the brain and spinal cord. Common symptoms of meningitis include fever, headache, vomiting, nausea, confusion, fatigue, stiff neck, sensitivity to light, decreased appetite, and skin rash.
  • Autoimmune disorders: A group of nonspecific symptoms, including fatigue, dizziness, general feeling of discomfort, and fever, often accompany autoimmune diseases.
  • Autoimmune disorders typically lead to the destruction of an organ or tissue, which results in decreased function of the affected organ or tissue. For instance, cells in the pancreas are destroyed in diabetic patients. Many autoimmune disorders also cause the organ or tissue to enlarge. For instance, Grave's disease causes thyroid enlargement (goiter formation).

  • General: If a complement deficiency is suspected, a blood test called a complement assay may be performed to confirm a diagnosis. If a patient tests positive for complement deficiency, a DNA analysis may be performed to determine if the disorder is genetic. Pregnant mothers who inherited the disorder or are carriers of the disease may have their fetuses tested for the disorder. If a patient tests positive for complement deficiency, a fluorescent antinuclear antibody test (FANA) may be conducted to determine whether the patient also has an autoimmune disorder.
  • Complement assay: A complement assay is a type of blood test used to determine if a patient has a complement deficiency. A small sample of blood is drawn from the patient's vein. The blood sample is then analyzed to determine how much protein is present and how well is it functioning. Complement deficiency is diagnosed if the patient has low or nonexistent levels of one or more complement proteins.
  • DNA analysis: A DNA analysis may be used to determine whether a patient has inherited a complement disorder. However, some patients develop the disorder as a result of another medical condition. Therefore, this test should not be used alone to diagnose complement deficiencies.
  • During the procedure, a small sample of the patient's blood is sent to a laboratory that performs genetic testing. The sample is then analyzed for the presence of genes that are associated with the disorder.
  • Fluorescent antinuclear antibody test (FANA): The fluorescent antinuclear antibody test (FANA) is a blood test used to detect abnormal antibodies, called autoantibodies. The autoantibodies bind to components of and individual's own cells and cause the immune system to attack the body.
  • During the procedure, a small sample of blood is taken from the patient and sent to a laboratory. The scientist adds methyl alcohol to a microscope slide that contains human tissue culture cells. This makes the cells permeable before they are combined with the patient's blood.
  • Then the patient's blood is added to the microscope slide. Fluorescent antibodies that detect the binding of human antibodies to the cells are also added. The scientist uses a fluorescent microscope to view the staining intensity and binding pattern of the cells. If autoantibodies are detected, a positive diagnosis is made for an autoimmune disorder.
  • If a patient has a positive FANA result, further testing may be needed to diagnose the specific type of autoimmune disorder. In some cases, the patient's symptoms and FANA results are enough to diagnose a specific condition.
  • In rare occasions, the FANA test results can be positive in people who do not have autoimmune disease. This is called a false positive test result. The frequency of false-positive test results increases with age. A false negative result is also possible, but it is also uncommon.
  • Prenatal DNA analysis: Pregnant mothers may have their unborn children tested for genetic disorders. In order to retrieve a sample of the fetus' cells for testing, amniocentesis or chorionic villus sampling may be performed. During amniocentesis, a long, thin needle is inserted into the pregnant woman's abdominal wall to the uterus. A small amount of fluid is removed from the sac surrounding the fetus. During chorionic villus sampling (CVS), a small piece of tissue (chorionic villi) is removed from the placenta for genetic testing. There are risks associated with these procedures, including miscarriage. Patients should discuss the potential risks and benefits of these procedures their healthcare providers.

  • General: There is currently no cure for complement deficiencies. Instead, patients receive medications called antimicrobials for infections and/or drugs called immunosuppressants for autoimmune disorders. If the complement deficiency develops as a result of another medical condition, such as liver disease, the disorder will be cured once the underlying cause is treated.
  • Patients should tell their healthcare providers if they are taking any drugs (prescription or over-the-counter), herbs, or supplements because they may interact with treatments. Also, patients should take medications exactly as prescribed by their doctors. If antimicrobials are discontinued too quickly, the infection may return.
  • Antimicrobials: Antimicrobial medications are used to treat infections commonly associated with complement deficiencies. Antibiotics are used to treat bacterial infections. Antifungals are used to treat fungal infections. Antivirals are used to treat fungal infections. Depending on the type and severity of the condition, these drugs may be applied to the skin, injected into a vein, or taken by mouth. The length of treatment and specific dosages also depend on the type and severity of the infection.
  • Immunosuppressants: Patients who have autoimmune disorders receive immunosuppressants, such as azathioprine (Imuran®, Azasan®). These medications help reduce the immune response against normal body tissue. This treatment helps reduce symptoms of autoimmunity and helps prevent the immune system from damaging organs. The lowest effective dose should be used because immunosuppressants further weaken the body's immune system, making the patient even more vulnerable to infections.
  • Intravenous immunoglobulin transfusion (IVIG): Intravenous immunoglobulin transfusion (IVIG) has been used to reduce to control the autoimmune process and to boost the body's ability to fight disease. IVIG is made of antibodies extracted from pooled blood donations from hundreds to thousands of donors. IVIG, such as Gamimune N®, Gammagard S/D® or Sandoglobulin®, is typically injected into the patient's vein for about two to four hours a day for two to seven days. The patient usually receives another single dose every 10-21 days or every three to four weeks, depending on the severity of the condition.

Integrative therapies
  • Good scientific evidence:
  • Probiotics: Probiotics are beneficial bacteria that are sometimes called friendly germs. They help maintain a healthy intestine and aid in digestion. They also help keep harmful bacteria and yeasts in the gut under control. Most probiotics come from food sources, especially cultured milk products. Probiotics can be taken as capsules, tablets, beverages, powders, yogurts, and other foods. Limited evidence with day care children suggests supplementation with Lactobacillus GG may reduce number of sick days, frequency of respiratory tract infections, and frequency of related antibiotic treatments. Fermented milk (with yogurt cultures and L. casei DN-114001) may reduce the duration of winter infections (gastrointestinal and respiratory), as well as average body temperature, in elderly people.
  • Probiotics are generally considered safe and well tolerated. Avoid if allergic or hypersensitive to probiotics. Use cautiously if lactose intolerant.
  • Unclear or conflicting scientific evidence:
  • Blessed thistle: Blessed thistle leaves, stems, and flowers have traditionally been used in "bitter" tonic drinks and other preparations that are taken by mouth to enhance appetite and digestion. Blessed thistle may also be included in the unproven anti-cancer herbal remedy Essiac®. Laboratory studies report that blessed thistle and some chemicals in blessed thistle may help fight against several types of bacteria, but have no effects on some types. Reliable human study is lacking. Further evidence is necessary in this area before a firm conclusion can be drawn.
  • Avoid if allergic to blessed thistle, mugwort, bitter weed, blanket flower, chrysanthemum, coltsfoot, daisy, dandelion, dwarf sunflower, goldenrod, marigold, prairie sage, ragweed, echinacea, or any plants of the Asteraceae or Compositae families. Avoid with history of bleeding diseases or gastroesophageal reflux disease (GERD), or if taking drugs for blood thinning, stroke, stomach diseases, or to control stomach acid. Avoid if pregnant or breastfeeding. Stop use two weeks before surgery/dental/diagnostic procedures with bleeding risk and do not use immediately after these procedures.
  • Cranberry: Cranberries come from small evergreen shrubs with tart, red, edible berries. The berries are used in sauces, jellies, and drinks. Study results of cranberry as an antibacterial in other conditions show conflicting results. Further study is needed before a conclusion can be drawn.
  • Avoid if allergic to cranberries, blueberries, or other plants of the Vaccinium species. Sweetened cranberry juice can affect blood sugar levels. Use cautiously with history of kidney stones. Avoid more than the amount usually found in foods if pregnant or breastfeeding.
  • Garlic: The Garlic bulb is made of many cloves wrapped with a paper-thin, white skin. Fresh or dehydrated garlic is used both medicinally and as a spice in foods. Several studies describe the application of garlic to the skin to treat fungal infections, including yeast infections. Use cautiously because garlic can cause severe burns and rash when applied to the skin of sensitive individuals.
  • Preliminary research suggests potential benefits of oral plus intravenous garlic in the management of cryptococcal meningitis. Further research is needed before a firm conclusion can be made.
  • Avoid if allergic or hypersensitive to garlic or other members of the Lilaceae(lily) family (such as hyacinth, tulip, onion, leek, chive). Avoid with history of bleeding problems, asthma, diabetes, low blood pressure, or thyroid disorders. Stop using supplemental garlic two weeks before dental/surgical/diagnostic procedures and avoid using immediately after such procedures to avoid bleeding problems. Avoid in supplemental doses if pregnant or breastfeeding.
  • Lavender: Lavender is native to the Mediterranean Peninsula, Arabian Peninsula, Russia, and Africa. Today, lavender is cultivated around the world. Oils from the flowers are used in aromatherapy, baked goods, candles, cosmetics, detergents, jellies, massage oils, perfumes, powders, shampoo, soaps, and tea. Early laboratory studies suggest that lavender oils may have antibiotic activity. However, this has not been well tested in animal or human studies.
  • Avoid if allergic or hypersensitive to lavender. Avoid with a history of seizures, bleeding disorders, eating disorders (anorexia, bulimia), or anemia (low levels of iron). Avoid if pregnant or breastfeeding.
  • Probiotics: Probiotics are beneficial bacteria that are sometimes called friendly germs. They help maintain a healthy intestine and aid in digestion. They also help keep harmful bacteria and yeasts in the gut under control. Most probiotics come from food sources, especially cultured milk products. Probiotics can be taken as capsules, tablets, beverages, powders, yogurts, and other foods. There is limited evidence that probiotic supplementation may reduce the presence of harmful bacteria in the upper respiratory tract. More studies are needed to establish this relationship and its implications for health.
  • Probiotics are generally considered safe and well tolerated. Avoid if allergic or hypersensitive to probiotics. Use cautiously if lactose intolerant.
  • Propolis: Bees produce a natural resin called propolis to make their hives. Propolis is made from the buds of conifer and poplar tress, and it is combined with beeswax and other bee secretions. Today, propolis is commonly found in chewing gum, cosmetics, creams, cough drops, and ointments. Laboratory studies report antiviral activity of propolis. It has shown to help fight against viral infections, such as herpes simplex virus types 1 and 2. Preliminary results from poorly designed human studies suggest propolis used on the skin may improve lesions from genital herpes virus infections. However, without better human study, including comparisons to prescription drugs, firm conclusions cannot be drawn.
  • Animal and laboratory studies suggest activity of propolis in the treatment of various types of infections. Initial human research reports possible benefits against oral/dental bacteria, genital herpes, urine bacteria, intestinal giardia infections, or H. pylori. Additional research is needed before a recommendation can be made.
  • Avoid if allergic or hypersensitive to propolis, black poplar (Populas nigra), poplar bud, bee stings, bee products, honey, and Balsam of Peru. Severe allergic reactions have been reported. There has been one report of kidney failure with the ingestion of propolis that improved upon discontinuing therapy, and deteriorated with re-exposure. Avoid if pregnant or breastfeeding because of the high alcohol content in some products.
  • Seaweed, kelp, bladderwrack: Bladderwrack (Fucus vesiculosus) is a brown seaweed found along the northern coasts of the Atlantic and Pacific oceans and North and Baltic seas. Another seaweed that grows alongside bladderwrack is Ascophyllum nodosum, and itis often combined with bladderwrack in kelp preparations. Laboratory study suggests antifungal and antibacterial activity of bladderwrack. However, there are no reliable human studies to support use as an antibacterial or antifungal agent.
  • Avoid if allergic or hypersensitive to Fucus vesiculosus and iodine. Avoid with history of thyroid disease, bleeding, acne, kidney disease, blood clots, nerve disorders, high blood pressure, stroke, or diabetes. Avoid if pregnant or breastfeeding.
  • Selenium: Selenium is a mineral found in soil, water and some foods. Preliminary research reports that selenium can be beneficial in the prevention of several types of infection, including recurrence of erysipelas (bacterial skin infection associated with lymphedema) or Mycoplasma pneumonia. Further research is needed to confirm these results before a clear conclusion can be made.
  • Avoid if allergic or sensitive to products containing selenium. Avoid with history of non-melanoma skin cancer. Selenium is generally regarded as safe for pregnant or breastfeeding women. However, animal research reports that large doses of selenium may lead to birth defects.
  • Sorrel: Sorrel has been used as a salad green, spring tonic, diarrhea remedy, weak diuretic (to help eliminate water from the body), and a soothing agent for sore noses. In Turkey, it is used to treat anemia and increase appetite. Sorrel is one of the main ingredients in the combination herbal cancer remedy Essiac® and in the European combination herbal sinus remedy Sinupret®. There are no well-conducted published studies that demonstrate sorrel to possess activity against viruses or bacteria that can infect humans. Further research is needed in this area.
  • Avoid sorrel if allergic to sorrel or any member of the Rumex acetosa or Polygonaceae plant families. Avoid large doses of sorrel because there have been reports of toxicity and death, possibly caused by oxalate found in sorrel. Fatal oxalic acid poisoning has been reported from sorrel soup. Be aware that many tinctures contain high levels of alcohol and should be avoided when driving or operating heavy machinery. These sorrel formulations may cause nausea or vomiting when taken with the prescription drugs metronidazole (Flagyl®) or disulfiram (Antabuse®). Avoid if pregnant or breastfeeding.

  • DNA analysis: Patients who are suspected carriers of complement deficiencies can undergo genetic testing to determine whether they have the mutated gene. Although carriers do not have the disorder, they may pass the mutated gene to their children.
  • Genetic counseling: Patients who have complement deficiencies may wish to receive genetic counseling. A counselor will provide information and answer questions about the risk of passing the disorder on to the patient's children. Genetic counseling is also available before and after a genetic test is performed.
  • Good hygiene: Patients can take precautions to avoid contracting infections associated with the disorder. Patients should thoroughly wash their hands with soap and water, especially after close contact with individuals who have contagious infections. Patients should minimize or avoid close contact with individuals who have contagious illnesses.
  • Vaccines: Patients should talk with their healthcare providers about recommended vaccines to prevent infections. In general, the meningitis, pneumonia, and flu vaccine are recommended.

Copyright © 2011 Natural Standard (

The information in this monograph is intended for informational purposes only, and is meant to help users better understand health concerns. Information is based on review of scientific research data, historical practice patterns, and clinical experience. This information should not be interpreted as specific medical advice. Users should consult with a qualified healthcare provider for specific questions regarding therapies, diagnosis and/or health conditions, prior to making therapeutic decisions.

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