antibody

Examples of antibody in the following topics:

• Antibody Structure

  • Variations in antibody structure allow great diversity of antigen recognition among different antibodies.
  • The constant domain, which does not bind to an antibody, is the same for all antibodies.
  • The large diversity of antibody structure translates into the large diversity of antigens that antibodies can bind and recognize.
  • Ig stands for immunoglobulin, another term for an antibody.
  • Prior to antibody secretion, plasma cells assemble IgM molecules into pentamers (five individual antibodies) linked by a joining (J) chain .

• Antibody Functions

  • Sometimes, antibodies can be transferred from one individual to another.
  • Phagocytic enhancement by antibodies is called opsonization.
  • In fact, antibodies exhibit different affinities (attraction) depending on the molecular complementarity between antigen and antibody molecules .
  • Typically, multimeric antibodies, such as pentameric IgM, are classified as having lower affinity than monomeric antibodies, but high avidity.
  • (b) An antibody may cross-react with different epitopes.

• Humoral Immune Response

  • An antigen is a biomolecule, such as a protein or sugar, that binds to a specific antibody.
  • An antibody/antigen interaction may stimulate an immune response.
  • Antibodies are the agents of humoral immunity.
  • Antibodies occur in the blood, in gastric and mucus secretions, and in breast milk.
  • Antibody neutralization can prevent pathogens from entering and infecting host cells.

• The Complement System

  • The complement system is so named because it is complementary to the antibody response of the adaptive immune system.
  • Complement proteins bind to the surfaces of microorganisms and are particularly attracted to pathogens that are already bound by antibodies.
  • The classic pathway for the complement cascade involves the attachment of several initial complement proteins to an antibody-bound pathogen, followed by rapid activation and binding of many more complement proteins and the creation of destructive pores in the microbial cell envelope and cell wall.
  • The alternate pathway does not involve antibody activation.

• Hypersensitivities

  • Upon initial exposure to a potential allergen, an allergic individual synthesizes antibodies of the IgE class; this class of antibodies also mediates the immune response to parasitic worms.
  • Antibodies that inappropriately mark self components as foreign are termed autoantibodies.
  • Antibodies and TCRs may bind self antigens that are structurally similar to pathogen antigens, which the immune receptors first raised.
  • These antibodies can damage heart muscle with autoimmune attacks, leading to rheumatic fever.
  • On first exposure to an allergen, an IgE antibody is synthesized by plasma cells in response to a harmless antigen.

• Immunological Memory

  • During the adaptive immune response to a pathogen that has not been encountered before, known as the primary immune response, plasma cells secreting antibodies and differentiated T cells increase, then plateau over time.
  • Memory B cells that differentiate into plasma cells output ten to hundred-fold greater antibody amounts than were secreted during the primary response .
  • This rapid and dramatic antibody response may stop the infection before it can even become established.
  • In the primary response to infection, antibodies are secreted first from plasma cells.
  • Upon re-exposure to the same pathogen, memory cells differentiate into antibody-secreting plasma cells that output a greater amount of antibody for a longer period of time.

• Plasma and Serum

  • The plasma also contains the coagulation factors and antibodies.
  • Other components in the serum include proteins, which assist with maintaining pH and osmotic balance while giving viscosity to the blood; antibodies, or specialized proteins that are important for defense against viruses and bacteria; lipids, including cholesterol, which are transported in the serum; and various other substances including nutrients, hormones, metabolic waste, and external substances, such as drugs, viruses, and bacteria.
  • Immunoglobin, a protein antibody produced in the mucosal lining, plays an important role in antibody mediated immunity.

• Antigen-presenting Cells: B and T cells

  • An antigen is a molecule that binds to a specific antibody, often stimulating a response in the immune system as a result.
  • Their attack can kill pathogens directly or they can secrete antibodies that enhance the phagocytosis of pathogens and disrupt the infection.
  • On B cells, these receptors contain antibodies, which are responsible for antigen binding .
  • An antibody is specific for one particular antigen; typically, it will not bind to anything else.
  • B cell receptors are embedded in the membranes of B cells and bind a variety of antigens through their variable regions, or antibodies.

• Basic Techniques in Protein Analysis

  • The western blot, or protein immunoblot, is a technique that combines protein electrophoresis and antibodies to detect proteins in a sample.
  • The protein sample is first separated by gel electrophoresis, then transferred to a nitrocellulose or other type of membrane, and finally stained with a primary antibody that specifically binds the protein of interest.
  • A fluorescent or radioactive-labeled secondary antibody binds to the primary antibody and provides a means of detection via either photography or x-ray film, respectively.

• Cytotoxic T Lymphocytes and Mucosal Surfaces

  • Antibodies are synthesized and secreted by activated plasma cells in the spleen, which filters foreign substances and antibody-complexed pathogens from the blood.