Vaccine Model Antigens (Ovalbumin, DNP, and DNA) ELISA Kits and Reagents

The immune system is a system of biological structures and processes within an organism that protects against disease. To function properly, an immune system must detect a wide variety of agents, from viruses to parasitic worms, and distinguish them from the organism's own healthy tissue.  If a pathogen breaches these barriers, the innate immune system provides an immediate, but non-specific response.  Innate immune systems are found in all plants and animals.  If pathogens successfully evade the innate response, vertebrates possess a second layer of protection, the adaptive immune system, which is activated by the innate response.  Here, the immune system adapts its response during an infection to improve its recognition of the pathogen. This improved response is then retained after the pathogen has been eliminated, in the form of an immunological memory, and allows the adaptive immune system to mount faster and stronger attacks each time this pathogen is encountered.  Disorders of the immune system can result in autoimmune diseases, inflammatory diseases and cancer.  White blood cells or immune cells are cells of the immune system involved in defending the body against both infectious disease and foreign materials.  Immunoglobulins (Ig's) or antibodies are major components of the immune system. Antibodies are secreted by a type of white blood cell called a plasma cell.  Activated B cells differentiate into either antibody-producing cells called plasma cells that secrete soluble antibody or memory cells that survive in the body for years afterward in order to allow the immune system to remember an antigen and respond faster upon future exposures.  T helper cells (Th cells) are a sub-group of lymphocytes that play an important role in the immune system, particularly in the adaptive immune system.  They are essential in B cell antibody class switching, in the activation and growth of cytotoxic T cells, and in maximizing bactericidal activity of phagocytes such as macrophages.

Five different antibody isotypes (IgA, IgD, IgE, IgG, and IgM) are known in mammals.  IgG subclasses are defined by the type of heavy chains.  Antibody isotypes perform different roles and help direct the appropriate immune response for each different type of foreign object they encounter.  Immunoglobulin class switching recombination (CSR)) is a biological mechanism that changes a B cell's production of antibody from one class to another.  There are four IgG subclasses in humans, named in order of their abundance in serum: IgG1 (66%), IgG2 (23%), IgG3 (7%), and IgG4 (4%).  The IgG2 in mouse is subdivided into IgG2a and IgG2b. Antibodies can occur in two physical forms, a soluble form that is secreted from the cell, and a membrane-bound form that is attached to the surface of a B cell and is referred to as the B cell receptor (BCR).  The basic functional unit of each antibody is an immunoglobulin_lifetech_india (Ig) monomer; secreted antibodies can also be dimeric with two Ig units as with IgA or pentameric IgM.  Antibodies are ~150 kDa globular plasma proteins containing two identical class γ heavy chains of about 50 kDa and two identical light chains of about 25 kDa.  Each IgG has two antigen binding sites.  Representing approximately 75% of serum immunoglobulin_lifetech_india in humans, IgG is the most abundant antibody isotype found in the circulation allowing it to control infection of body tissues.  By binding many kinds of pathogen-representing viruses, bacteria, and fungi-IgG protects the body from infection.  It does this via several immune mechanisms: IgG-mediated binding of pathogens causes their immobilization and binding together via agglutination; IgG coating of pathogen surfaces allows their recognition and ingestion by phagocytic immune cells; IgG activates the classical pathway of the complement system, a cascade of immune protein production that results in pathogen elimination; IgG binds and neutralizes toxins.  IgG also plays an important role in antibody-dependent cell-mediated cytotoxicity (ADCC).  It is associated with Type II and Type III Hypersensitivity.  IgG antibodies are generated following class switching and maturation of the antibody response and thus participate predominantly in the secondary immune response.  It is the only isotype that can pass through the human placenta, thereby providing protection to the fetus in utero. 

The functional activity of antibodies also depends on Ig's isotypes.  IgM is the first antigen receptor (BCR) made during B cell development and the first antibody secreted during an immune response.  Four subisotypes of IgG in humans have somewhat varied biological functions.  IgG is made later in a primary response than IgM, but it is produced more rapidly in a memory response. IgG is the predominant serum antibody with the longest half-life.  IgA is present in serum and predominates in mucosal secretions: breast milk, saliva, tears, and respiratory, digestive, and genital tract mucus. Secretory IgA provides a first-line defense where pathogens enter the body. More IgA is made than any other isotype.  IgG1 and IgG3 are most effective in complement binding and activation, and IgG2 may contribute to protection against disease.  Furthermore, affinity differences have been found in antibodies with similar antigen-binding specificities but different IgG isotypes. IgG1 and IgG3 are mainly directed at protein antigens, whereas IgG2 is predominantly found after vaccination with polysaccharide antigens in adults.  IgE produced in response to parasites and to allergens. Immunoglobulin D (IgD) is an antibody isotype that makes up about 1% of proteins in the plasma membranes of immature B-lymphocytes where it is usually co-expressed with another cell surface antibody called IgM.  IgD is also produced in a secreted form that is found in very small amounts in blood serum.

T cell cytokines are responsible for class switching.  In the mouse:

Th1 response mediated by macrophage (Cytokines: IFN-γ/IL-10/IL-2):  Isotypes (IgG2a)

Th2 response (Cytokines: IL-4, IL-5/6/10/13):  Isotypes (IgG1, IgE)

Treg response (Cytokines: TGFb) Isotypes (IgG2b, IgA)

Antibody response or isotype of an antibody is also influenced by the type of antigen (protein, bacteria, virus, or small molecule) immunization routes (intravenous, subcutaneous, intradermal etc), antigen dose and duration (amount of the antigen and frequency of exposure, and multiplicity of immunization) and the presence of other agents in the antigens (proteins, DNA, and adjuvants etc).  Adjuvants (Squalene, Alhydrogel, Incomplete Freunds adjuvant) primarily invoke Th2 response whereas TLR5 agonist (Flagellin, CpG ODNs type A/B/C, Poly I/C or dsDNA induce Th1 reponse.  

A vaccine is a biological preparation that improves immunity to a particular disease.  A vaccine typically contains an agent that resembles a disease-causing microorganism, and is often made from weakened or killed forms of the microbe (bacteria or virus), its toxins or one of its antigenic proteins.  The immune system recognizes vaccine agents as foreign, destroys them, and "remembers" them. When the diseases causing or virulent version of an agent is encountered, the body recognizes the antigenic proteins on the bacteria or virus, and thus is prepared to respond, by (1) neutralizing the target agent before it can enter cells, and (2) by recognizing and destroying infected cells before that agent can multiply to vast numbers.  This is part of the adaptive (or acquired) immune response.  This process of acquired immunity is the basis of vaccination.  Success of a given vaccine depends upon its ability to produce high affinity, neutralizing antibodies with minimum exposure of the active vaccine ingredients (whole cells or bacteria or purified protein) and to provide long-term immunity.  Therefore, it is essential to study how antibody response and isotype are influenced by a given agent.  Ovalbumin (OVA also used as allergenic antigen, Bovine serum albumin (BSA, used model protein antigen) and Dinitrophenol (DNP, as hapten or small molecule antigen) have been used as "model antigens" to study antibody response.  In addition, these model antigens have also served to examine the immune-status of an individual or animal during a disease or as a result of exposure to a given drug. 

ADI has developed ELISA kits for various model antigens (ovalbumin, BSA, DNP, and DNA) to study basic mechanism of isotype switching and factors affecting it.