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Table of Contents > Allergies > Antigen-presenting cells Print

Antigen-presenting cells

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Also listed as: WAS
Related terms
Background
Author information
Bibliography
Macrophages
Dendritic cells
B-cells
Interaction with t-cells

Related Terms
  • Antibodies, auto recessive, B-cells, bone marrow, bone marrow transplant, CBC, genetic disorder, immune system, immunodeficiency, inherited disorder, inherited immunodeficiency, leukocytes, leukemia, lymphoma, lymphocytes, malignancy, platelets, pneumonia, red blood cells, T-cells, thrombocytes, thrombocytopenia, tumor, WASP, white blood cells, Wiskott Aldrich syndrome, Wiskott-Aldrich syndrome protein, X-linked.

Background
  • Wiskott-Aldrich syndrome (WAS) is an inherited, immunodeficiency disorder that occurs almost exclusively in males. The recessive genetic disorder is caused by a mutation in the WAS (Wiskott-Aldrich syndrome) gene, which is an X-linked trait. The gene mutation leads to abnormalities in B- and T-lymphocytes (white blood cells), as well as blood platelet cells. In a healthy individual, the T-cells provide protection against viral and fungal infection, the B cells produce antibodies, and platelets are responsible for blood clotting to prevent blood loss after a blood vessel injury.
  • Individuals diagnosed with WAS suffer from recurrent infections, eczema and thrombocytopenia (low levels of platelets).
  • Before 1935, patients only lived an average of eight months. Today, patients usually live an average of eight years, according to a recent case study. The cause of death is usually attributed to extensive blood loss. However, cancer (especially leukemia) is common and often fatal among WAS patients.
  • The only possible cure for WAS is a bone marrow transplant. However, if a patient's family member is not a possible match for a bone marrow donation, patients may have to wait years for a potential donor. Other aggressive treatments may also increase a patient's life expectancy. For instance, one study found that patients who underwent splenectomy (removal of the spleen) lived to be more than 25 years old. The spleen may harbor too many platelets, and cause a decrease in the number of platelets in circulation. Antibiotics, antivirals, antifungals, chemotherapeutic agents, immunoglobulins and corticosteroids have also been used to relieve symptoms and treat infections and cancer associated with WAS.
  • Researchers estimate that about four people per one million live male births develop the disease in the United States.
  • The syndrome is named after Dr. Robert Anderson Aldrich, an American pediatrician who described the disease in a family of Dutch-Americans in 1954, and Dr Alfred Wiskott, a German pediatrician who discovered the syndrome in 1937. Wiskott described three brothers with a similar disease, whose sisters were unaffected.

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

Bibliography
  1. Binder V, Albert MH, Kabus M, et al. The genotype of the original Wiskott phenotype. N Engl J Med. 2006 Oct 26;355(17):1790-3.
  2. Jin Y, Mazza C, Christie JR, et al. Mutations of the Wiskott-Aldrich Syndrome Protein (WASP): hotspots, effect on transcription, and translation and phenotype/genotype correlation. Blood. 2004 Dec 15;104(13):4010-9. Epub 2004 Jul 29.
  3. Natural Standard: The Authority on Integrative Medicine. .
  4. St. Jude Children's Research Hospital. Inherited Immunodeficiencies: Wiskott-Aldrich Syndrome (WAS). .
  5. U.S. Immune Deficiency Foundation. The Wiskott Aldrich Syndrome. .

Macrophages
  • Macrophages are white blood cells that are found inside the tissues of all vertebrates. These cells originate from monocytes in the bone marrow. Macrophages are phagocytes, which means they are able to engulf antigens that enter the body. The lifespan of macrophages ranges from months to years, and they can digest more than 100 bacteria before they die.
  • Macrophages are in a resting state until they are activated by an immune response. Upon activation, these cells travel toward the site of injury, and they engulf pathogens. Once a macrophage ingests a pathogen, the pathogen is trapped inside the cell's food vacuole, which then fuses with a lysosome. Enzymes and toxic peroxides inside the cell start to ingest the foreign substance. The cells then secrete interferons, lysozyme and other factors that stimulate lymphocytes and other immune cells to respond to the antigens.
  • During chronic inflammation, macrophages can form granulomas (inflammatory lesions). They are also the predominant cells that form the progressive plaque lesions associated with atherosclerosis (hardening of the arteries).

Dendritic cells
  • Dendritic cells are present in small amounts in the body tissues that frequently come into contact with the external environment. They are present in the skin (where they are often called langerhans cells) and the inner lining of the nose, stomach, lungs and intestines. These cells have branched projections, called dendrites.
  • Immature dendritic cells (also called veiled cells) are found in the bloodstream. Immature dendritic cells are characterized by high endocytic activity and low T-cell activation potential. Their pattern recognition receptors (PRRs) are constantly sampling their surroundings for pathogens, such as bacteria and viruses. Once the dendritic cell comes into contact with a pathogen, they are activated to engulf the invading substance. Once the antigen is engulfed, the dendritic cell matures and combines the broken down antigen with MHC. This complex is then presented to T-cells on its cell surface.

B-cells
  • Unlike the other two APCs, they produce antibodies (immunoglobulin) that are specific to certain antigens. B-cells are able to efficiently present the antigen to which their antibody is directed, but they are considered inefficient APCs for most other antigens.
  • B-cells are continually produced in the bone marrow. Immature B-cells only express IgM on their cell membrane. The immunoglobulin is on the cell surface. It is not secreted.
  • Once the B-cell reaches maturity, it can express both IgM and IgD on the cell surface. This mature cell is now able to respond to antigens. If the B-cell starts to mature abnormally, it will die in a process called apoptosis (programmed cell death).
  • Once the immunoglobulin molecule interacts with an antigen, the B-cell becomes activated and begins to divide and differentiate into many antibody-producing cells (plasma cells). Each plasma cell secretes millions of identical antibody molecules, which are released into the bloodstream.
  • Some of the plasma cells undergo isotype switching. During this process, the cell starts to express other isotypes of immunoglobulin, including IgA, IgE and IgG.

Interaction with t-cells
  • Once APCs engulf pathogens, they usually migrate toward the lymph nodes, where most T-cells are located. They migrate chemotactically, which means that chemokines (chemical mediators in the blood that are produced by cytokines) attract the APCs to move toward the lymph nodes.
  • During the migration, the APC cells mature. They lose most of their ability to engulf pathogens, and they develop an increased ability to communicate with T-cells.
  • Enzymes inside the APC cell digest the engulfed pathogen into smaller pieces, which contain epitopes (part of a foreign substance that can be recognized by the immune system). These epitopes are combined with MHC and presented to the T-cells on their cell surface.
  • The helper T-cell then activates the APC to produce more antibodies against the pathogen.
  • Recent research suggests that only certain epitopes of an antigen are presented by they APC because they are immunodominant. This may be the result of their binding affinity to the MHC molecule. The stronger binding affinity allows the complex to remain kinetically stable long enough for the T-cells to recognize it.

Copyright © 2011 Natural Standard (www.naturalstandard.com)


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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