Antigen altered processing

Penicillin is an unstable, reactive molecule which in the body can easily react with constituents of the cells and tissues such as proteins. The reaction with proteins will alter their structure. They may become sufficiently different to be recognized by the immune system, and the body then mounts an immune attack on these altered proteins (known as antigens). This process can take one of several forms. For example, if the penicillin reacts with the proteins on the outside of the red blood cell, these may be recognized by the immune system. The immune system then reacts by producing antibodies, specific proteins which will recognize and bind to the altered red cells. The next stage is when a type of white blood cell called a natural killer cell sees and binds to the antibody on the red cell and destroys the red cell. The result of this is haemolytic anaemia, in which the number of red blood cells is depleted, possibly to dangerous levels. 

Second, the reactive species of a xenobiotic may bind to a protein, altering its antigenicity. The xenobiotic is said to act as a hapten, ie, a small molecule that by itself does not stimulate antibody synthesis but will combine with antibody once formed. The resulting antibodies can then damage the cell by several immunologic mechanisms that grossly perturb normal cellular biochemical processes. 

An alteration in the inflammatory response regulated by intestinal epithelial cells may also contribute to development of IBD. This may involve inappropriate processing of antigens presented to the GI epithelial cells.3 The inflammatory response in IBD may actually be directed at bacteria that normally colonize... 

Opsonization The process by which an antigen is altered so as to become more readily and more efficiently engulfed by phagocytes. 

The antiproliferative effects of arsenic are well documented. In vitro both divalent and pentavalent arsenicals inhibit murine [28] and bovine [18] phytohemaglutinin (PHA)-stimulated lymphoproliferation at concentrations of > 3 pM. Lymph node cells from arsenic treated, FTTC-sensitized mice displayed reduced lymphoproliferation in response to Con A, suggesting that the mechanism of antigen processing/presentation may be altered by arsenic exposure, inhibiting T-cell responsiveness [29], However, in vivo... 

Product variants can also be generated by in-process procedures, such as those used for viral inactivation, for example. These procedures could alter the protein structure, forming new epitopes. These types of changes could potentially be detected by ELISA because of the specificity of the antigen-antibody interaction. In the case of vaccine production, an ELISA could be used to monitor viral inactivation. For this, a panel of MAbs, if available, could be used. 

Different mechanisms can lead to total or partial loss of HLA class 1 antigen expression. This could occur at any step of the MHC class 1 processing machinery and involves structural alterations, epigenetic mechanisms and dysregulation of various APM components. 

Seliger, B., Ritz, U., Abele, R., Bock, M., Tampe, R., Sutter, G., Drexler, I., Huber, C., and Ferrone, S., 2001, Immune escape of melanoma First evidence of structural alterations in two distinct components of the MHC class 1 antigen processing pathway. Cancer Res. 61 8647-8650. 

Affinity maturation of antibodies has been achieved by the introduction of diversity into the V-genes, which then creates diversity within the antigen binding sites. This secondary library is then subjected to a selection that will enrich high affinity variants. More or less random diversity may be introduced by altering variable domain pairings in a process called... 

Proteasomes of Thermoplasma contain a single type of p subunit but eukaryotic proteasomes contain subunits with at least three distinct substrate preferences.347 M9c They all appear to use the same hydrolytic mechanism but in their substrate specificities they are chymotrypsin-like, peptidylglutamyl-peptide hydrolyzing, branched chain amino acid preferring, and small neutral amino acid preferring based on the P, amino acid residue. In the spleen some of the P subunits of the proteasomes appear to have been replaced by proteins encoded by the major histocompatibility complex of the immune system (Chapter 31).347 This may alter the properties of the proteasome to favor their function in antigen processing. Proteasomes are also ATP- and ubiquitin-dependent, as discussed in Section 6. 

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