Autoimmune Diseases: Experimental Therapy with Protein A.

Dmitri Popov. PhD, Radiobiology. MD (Russia)Advanced Medical Technology and Systems Inc. Canada.

Autoimmune Diseases: Experimental Therapy with Protein A. ELECTIVE IMMUNOSUPPRESSION.Protein AProtein Ais a 42kDasurfaceproteinoriginally found in the cell wall of thebacteriumStaphylococcus aureus. It is encoded by the spagene and its regulation is controlled by DNA topology, cellular osmolarity, and atwo-component systemcalled ArlS-ArlR. It has found use in biochemical research because of its ability to bindimmunoglobulins.

Protein A.

Protein A. It is composed of five homologous Ig-binding domains that fold into a three-helix bundle. Each domain is able to bind proteins from many mammalian species, most notablyIgGs. It binds the heavy chain within theFc regionof most immunoglobulins and also within theFab regionin the case of the human VH3 family. Through these interactions in serum, where IgG molecules are bound in the wrong orientation (in relation to normalantibodyfunction), the bacteria disruptsopsonizationandphagocytosis.Protein A. Purified (unconjugated) Thermo Scientific Pierce Recombinant Protein A is useful as the basis for preparing various kinds of probes or affinity media for detection or purification of rabbit and human antibodies, especially IgG isotypes, in immunoassays and antibody purification protocols.

Features of Recombinant Protein A:

Contains four Fc-binding domains per protein Better than Protein G for polyclonal IgG from rabbit, pig, dog and cat serum Poorer than Protein G for mouse IgG1, human IgG3 and rat, goat and cow antibodies

Protein A.Protein A is a cell wall component produced by several strains ofStaphylococcus aureusthat consists of a single polypeptide chain and contains little or no carbohydrate. Recombinant Protein A is produced inE. coliand functions essentially the same as native Protein A. The Protein A molecule contains four high-affinity binding sites capable of interacting with the Fc region from IgG of several species including human and rabbit. Optimal binding occurs at pH 8.2, although binding is also effective at neutral or physiological conditions (pH 7.0 to 7.6).Protein A. The interaction between Protein A and IgG is not equivalent for all species. Even within a species, Protein A interacts with some subclasses of IgG and not others. For instance, human IgG1, IgG2 and IgG4 bind strongly, while IgG3 does not bind. There are also many instances in which monoclonal antibodies do not bind to Protein A, especially the majority of rat immunoglobulins and mouse IgG1.Protein A.Properties of Recombinant Protein A: Source:E. coli Molecular Weight: ~44,600 (Apparent MW by SDS-PAGE: 45,000) Form: salt-free powder A280 of 0.1% solution: ~0.165 Isoelectric point (pI): 4.7-4.8

Related ProductsPierce Recombinant Protein A, Peroxidase ConjugatedProtein A. https://www.lifetechnologies.com/order/catalog/product/21184Protein A.https://tools.lifetechnologies.com/content/sfs/manuals/MAN0011438_Pierce_Ig_Bind_Proteins_UG.pdfhttps://tools.lifetechnologies.com/content/sfs/brochures/TR0034-Ab-binding-proteins.pdf

Protein A. Crystal structure of aStaphylococcus aureusprotein A domain complexed with the Fab fragment of a human IgM antibody: Structural basis for recognition of B-cell receptors and superantigen activityMarc Graille et al. Proc Natl Acad Sci U S A. 2000 May 9; 97(10): 53995404.PMCID:PMC25840Immunology

Protein A.Staphylococcus aureusproduces a virulence factor, protein A (SpA), that contains five homologous Ig-binding domains. The interactions of SpA with the Fab region of membrane-anchored Igs can stimulate a large fraction of B cells, contributing to lymphocyte clonal selection.Protein A.Staphylococcus aureusProtein A Promotes Immune SuppressionScott D. Kobayashi,Frank R. DeLeo

Protein A.SpA binds the Fc region of antibody and the Fab regions of the B-cell receptor, processes that are known to block opsonophagocytosis and cause B-cell deathin vitro. In a recent study, Falugi et al. [F. Falugi, H. K. Kim, D. M. Missiakas, and O. Schneewind, mBio 4(5):e00575-13, 2013] showed that vaccination withspamutantS.aureusstrains lacking antibody Fc- and/or Fab-binding capacity protects against subsequent challenge with the USA300 epidemic strain. The findings provide strong support for the idea that SpA promotesS.aureusimmune evasionin vivoand form the foundation for a new approach in our efforts to develop a vaccine that prevents severeS.aureusinfections.Autoimmune Diseases.AUTOIMMUNE diseases, with the exception of rheumatoid arthritis and autoimmune thyroiditis, are individually rare, but together they affect approximately 5 percent of the population in Western countries.Mechanisms of Autoimmunity:Molecular Mimicry.Superantigenic Stimulation.Microbal Adjuvancticity.RadiationAutoimmune Diseases.Endogenous:Altered antigen presentation.1. Loss of immunologic privilige.2. Presentation of novel or crytic epitopes.3. Alteration of self-antigen4. Costumatory molecule expression5. Cytokine productionB. Increased T cell help:1. Cytokine production2. Costumatory moleculesAutoimmune Diseases.Increased B cell functionApoptotic defects.Cytokine imbalance.Altered Immunoregulation.Harrisons Principles of Internal Medicine.