antibodies

Examples of antibodies in the following topics:

• Fluorescent Antibodies

  • Fluorescent antibodies are antibodies that have been tagged with a fluorescent compound to facilitate their detection in the laboratory.
  • The fluorescent antibody technique consists of labeling antibody with dyes such as fluorescein isothiocyanate (FITC).
  • The chemical manipulation in labeling antibodies with fluorescent dyes to permit detection by direct microscopy examination does not impair antibody activity.
  • Fluorescent antibody conjugates are commonly used in immunoassays.
  • In the direct technique, a fluorescent antibody is used to detect antigen-antibody reactions at a microscopic level.

• Neutralization Reaction

  • Neutralization reactions are used to inactivate viruses and evaluate neutralizing antibodies.
  • This usually involves the formation of a virus-antibody complex.
  • This virus-antibody complex can prevent viral infections in many ways.
  • Antibodies can also neutralize viral infectivity by binding to cell surface receptors.
  • Neutralizing antibodies have shown potential in the treatment of retroviral infections.

• Antibody Genes and Diversity

  • Complex genetic mechanisms evolved which allow vertebrate B cells to generate a diverse pool of antibodies from relatively few antibody genes.
  • Virtually all microbes can trigger an antibody response.
  • Several complex genetic mechanisms have evolved that allow vertebrate B cells to generate a diverse pool of antibodies from a relatively small number of antibody genes.
  • Some point mutations will result in the production of antibodies that have a lower affinity with their antigen than the original antibody, and some mutations will generate antibodies with a higher affinity.
  • Schematic diagram of an antibody and antigens.

• Agglutination Reactions

  • Agglutination is the visible expression of the aggregation of antigens and antibodies.
  • These conjugated particles are reacted with patient serum presumably containing antibodies.
  • Flocculation tests are designed for antibody detection and are based on the interaction of soluble antigens with antibodies, producing a precipitate of fine particles that can be seen with the naked eye.
  • It measures the antibody level produced by a host infected with that pathogen.
  • Red blood cells are used as carriers to detect antibodies from a patient's serum.

• Complement Fixation

  • Complement fixation is a method that demonstrates antibody presence in patient serum.
  • Complement fixation is a classic method for demonstrating the presence of antibody in patient serum.
  • If the serum contains antibody to the antigen, the resulting antigen-antibody complexes will bind all of the complement.
  • Sheep red blood cells and the anti-sheep antibody are then added.
  • If complement has not been bound by an antigen-antibody complex formed from the patient serum and known antigens, it is available to bind to the indicator system of sheep cells and anti-sheep antibody.

• Antibody Proteins and Antigen Binding

  • A region at the tip of the antibody protein is very variable, allowing millions of antibodies with different antigen-binding sites to exist.
  • Antibodies are heavy (~150 kDa) globular plasma proteins.
  • Heavy and light chains, variable and constant regions of an antibody
  • The general structure of all antibodies is very similar.
  • Heavy and light chains, variable and constant regions of an antibody

• Immunoassays for Disease

  • Immunoassays are laboratory techniques based on the detection of antibody production in response to foreign antigens.
  • The humoral component includes complement, lyzozyme, interferon, antibodies, and cytokines.
  • Because antibodies can be produced against any type of macromolecule, antibody-based techniques are useful in identifying molecules in solution or in cells.
  • A blood sample is collected from the patient during the acute phase of the disease when antibody levels are high.
  • Serum is then isolated and the concentration of antibodies is measured through various methods.

• Isotype Class Switching

  • Antibodies can come in different varieties, known as isotypes or classes.
  • In placental mammals there are five antibody isotypes: IgA, IgD, IgE, IgG and IgM.
  • The antibody isotype of a B cell changes during cell development and activation.
  • B cell activation follows engagement of the cell-bound antibody molecule with an antigen, causing the cell to divide and differentiate into an antibody-producing cell, called a plasma cell.
  • During CSR, portions of the antibody-heavy chain locus are removed from the chromosome, and the gene segments surrounding the deleted portion are rejoined to retain a functional antibody gene that produces antibody of a different isotype.

• Passive Immunization

  • Artificial passive immunity is achieved by infusion of serum or plasma containing high concentrations of antibody.
  • This form of passive immunity provides immediate antibody protection against microorganisms such as hepatitis A by administering preformed antibodies.
  • Breast milk also contains antibodies, which means that babies who are breastfed have passive immunity for longer periods of time.
  • The thick, yellowish milk (colostrum) that is produced during the first few days after birth is particularly rich in antibodies.
  • Describe how artificial and natural passive immunity function to provide antibody protection against microorganisms

• Enzyme-Linked Immunosorbent Assay (ELISA)

  • ELISA uses a specific antibody with a covalently coupled enzyme.
  • A fixed quantity of one antibody is attached to a series of replicate solid supports, such as plastic microtiter multi-well plate.
  • Unbound antigen is removed by washing, and a second antibody which is linked to an enzyme is allowed to bind.
  • This second antibody-enzyme complex constitutes the indicator system of the test.
  • The antigen serves as bridge, so the more antigen in the test solution, the more enzyme-linked antibody will bind .