An immunogen is an antigen or any substance that may be specifically bound by components of the immune system (antibody, lymphocytes). The term antigen arises from its ability to induce generation of antibodies. Despite the fact that all antigens are recognized by specific lymphocytes or by antibodies, not every antigen can evoke an immune response. Those antigens that are capable of inducing an immune response are said to be immunogenic and are called immunogens.[1]
An immunogen is any antigen that is capable of inducing humoral and/or cell-mediated immune response rather than immunological tolerance. This ability is called immunogenicity. Sometimes the term immunogen is used interchangeably with the term antigen. But only an immunogen can evoke an immune response.[2]
Generally, both are substances that are capable of generating antibodies (antigen) or stimulating immune responses (immunogen).
We can define an immunogen as a complete antigen which is composed of the macromolecular carrier and epitopes (determinants) that can induce immune response.[3]
An explicit example is a hapten. Haptens are low-molecular-weight compounds that may be bound by antibodies, but cannot elicit an immune response. Consequently, the haptens themselves are nonimmunogenic and they cannot evoke an immune response until they bind with a larger carrier immunogenic molecule. The hapten-carrier complex, unlike free hapten, can act as an immunogen and can induce an immune response. [4]
Until 1959, the terms immunogen and antigen were not distinguished.[5]
Used carrier proteins[edit]
- It is copper-containing respiratory protein, isolated from keyhole limpets (Megathura crenulata). Because of its evolutionary distance from mammals, high molecular weight and complex structure it is usually immunogenic in vertebrate animals.[6]
- (also Blue Carrier Immunogenic Protein) It is alternative to KLH isolated from Concholepas concholepas. It has the similar immunogenic properties as KLH but better solubility and therefore better flexibility.[7]
- It is from the blood sera of cows and has similarly immunogenic properties as KLH or CCH. The cationized form of BSA (cBSA) is highly positively charged protein with significantly increased immunogenicity. This change possesses a greater number of possible conjugated antigens to the protein.[8]
- Also known as egg albumin, OVA is the main protein (60-75%) found in hen egg white. OVA is soluble in Dimethyl Sulfoxide (DMSO), which enables the conjugation of haptens that are not soluble in aqueous buffers. The immune response can be enhanced using an adjuvant injected together with the immunogen.[9]
Immunological adjuvants[edit]
- An adjuvant (from Latin adiuvare – to help) is any substance, distinct from antigen, which enhances immune response by various mechanisms: recruiting of professional antigen-presenting cells (APCs) to the site of antigen exposure; increasing the delivery of antigens by delayed/slow release (depot generation); immunomodulation by cytokine production (selection of Th1 or Th2 response); inducing T-cell response (prolonged exposure of peptide-MHC complexes [signal 1] and stimulation of expression of T-cell-activating co-stimulators [signal 2] on the APCs' surface) and targeting (e. g. carbohydrate adjuvants which target lectin receptors on APCs). Adjuvants have been used as additives to improve vaccine efficiency since the 1920s. Generally, administration of adjuvants is used both in experimental immunology and in clinical settings to ensure a high quality/quantity memory-enhanced antibody response, where antigens must be prepared and delivered in a fashion that maximizes production of a specific immune response. Among commonly used adjuvants are Complete and Incomplete Freund's adjuvant and solutions of aluminum hydroxide or aluminum phosphate.[10][11]
https://en.wikipedia.org/wiki/Immunogen
A latent infection may become productive in response to changes in the host's environmental conditions or health; the provirus may be activated and begin transcription of its viral genome. This can result in the destruction of its host cell because the cell's protein synthesis machinery is hijacked to produce more viruses.
Proviruses may account for approximately 8% of the human genome in the form of inherited endogenous retroviruses.[3][4]
A provirus not only refers to a retrovirus but is also used to describe other viruses that can integrate into the host chromosomes, another example being adeno-associated virus. Not only eukaryotic viruses integrate into the genomes of their hosts; many bacterial and archaeal viruses also employ this strategy of propagation. All families of bacterial viruses with circular (single-stranded or double-stranded) DNA genomes or replicating their genomes through a circular intermediate (e.g., tailed dsDNA viruses) have temperate members.[5]
An immune response is a reaction which occurs within an organism for the purpose of defending against foreign invaders. These invaders include a wide variety of different microorganisms including viruses, bacteria, parasites, and fungi which could cause serious problems to the health of the host organism if not cleared from the body.[1] There are two distinct aspects of the immune response, the innate and the adaptive, which work together to protect against pathogens. The innate branch—the body's first reaction to an invader—is known to be a non-specific and quick response to any sort of pathogen. Components of the innate immune response include physical barriers like the skin and mucous membranes, immune cells such as neutrophils, macrophages, and monocytes, and soluble factors including cytokines and complement.[2] On the other hand, the adaptive branch is the body's immune response which is catered against specific antigens and thus, it takes longer to activate the components involved. The adaptive branch include cells such as dendritic cells, T cell, and B cells as well as antibodies—also known as immunoglobulins—which directly interact with antigen and are a very important component for a strong response against an invader.[1]
The first contact that an organism has with a particular antigen will result in the production of effector T and B cells which are activated cells that defend against the pathogen. The production of these effector cells as a result of the first-time exposure is called a primary immune response. Memory T and memory B cells are also produced in the case that the same pathogen enters the organism again. If the organism does happen to become re-exposed to the same pathogen, a secondary immune response will kick in and the immune system will be able to respond in both a fast and strong manner because of the memory cells from the first exposure.[3] Vaccines introduce a weakened, killed, or fragmented microorganism in order to evoke a primary immune response. This is so that in the case that an exposure to the real pathogen occurs, the body can rely on the secondary immune response to quickly defend against it.[4]
https://en.wikipedia.org/wiki/Immune_response
Immune tolerance, or immunological tolerance, or immunotolerance, is a state of unresponsiveness of the immune system to substances or tissue that have the capacity to elicit an immune response in a given organism. It is induced by prior exposure to that specific antigen[1][2] and contrasts with conventional immune-mediated elimination of foreign antigens (see Immune response). Tolerance is classified into central tolerance or peripheral tolerance depending on where the state is originally induced—in the thymus and bone marrow (central) or in other tissues and lymph nodes(peripheral). The mechanisms by which these forms of tolerance are established are distinct, but the resulting effect is similar.
Immune tolerance is important for normal physiology. Central tolerance is the main way the immune system learns to discriminate self from non-self. Peripheral tolerance is key to preventing over-reactivity of the immune system to various environmental entities (allergens, gut microbes, etc.). Deficits in central or peripheral tolerance also cause autoimmune disease, resulting in syndromes such as systemic lupus erythematosus,[3] rheumatoid arthritis, type 1 diabetes,[4] autoimmune polyendocrine syndrome type 1 (APS-1),[5] and immunodysregulation polyendocrinopathy enteropathy X-linked syndrome (IPEX),[6] and potentially contribute to asthma, allergy,[7] and inflammatory bowel disease.[4] And immune tolerance in pregnancy is what allows a mother animal to gestate a genetically distinct offspring with an alloimmune response muted enough to prevent miscarriage.
Tolerance, however, also has its negative tradeoffs. It allows for some pathogenic microbes to successfully infect a host and avoid elimination.[8] In addition, inducing peripheral tolerance in the local microenvironment is a common survival strategy for a number of tumors that prevents their elimination by the host immune system.[9]
https://en.wikipedia.org/wiki/Immune_tolerance
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