Antigenic variation or antigenic alteration refers to the mechanism by which an infectious agent such as a protozoan, bacterium or virus alters the proteins or carbohydrates on its surface and thus avoids a host immune response, making it one of the mechanisms of antigenic escape. It is related to phase variation. Antigenic variation not only enables the pathogen to avoid the immune response in its current host, but also allows re-infection of previously infected hosts. Immunity to re-infection is based on recognition of the antigens carried by the pathogen, which are "remembered" by the acquired immune response. If the pathogen's dominant antigen can be altered, the pathogen can then evade the host's acquired immune system. Antigenic variation can occur by altering a variety of surface molecules including proteins and carbohydrates. Antigenic variation can result from gene conversion, site-specific DNA inversions, hypermutation, or recombination of sequence cassettes. The result is that even a clonal population of pathogens expresses a heterogeneous phenotype. Many of the proteins known to show antigenic or phase variation are related to virulence.
CD98 is a glycoprotein that is a heterodimer composed of SLC3A2 and SLC7A5 that forms the large neutral amino acid transporter (LAT1). LAT1 is a heterodimeric membrane transport protein that preferentially transports branched-chain and aromatic amino acids. LAT is highly expressed in brain capillaries relative to other tissues.
Complement receptor type 2 (CR2), also known as complement C3d receptor, Epstein-Barr virus receptor, and CD21, is a protein that in humans is encoded by the CR2 gene.
CD1D is the human gene that encodes the protein CD1d, a member of the CD1 family of glycoproteins expressed on the surface of various human antigen-presenting cells. They are non-classical MHC proteins, related to the class I MHC proteins, and are involved in the presentation of lipid antigens to T cells. CD1d is the only member of the group 2 CD1 molecules.
The complement component 1q is a protein complex involved in the complement system, which is part of the innate immune system. C1q together with C1r and C1s form the C1 complex.
CD46 complement regulatory protein also known as CD46 and Membrane Cofactor Protein is a protein which in humans is encoded by the CD46 gene. CD46 is an inhibitory complement receptor.
CD68 is a protein highly expressed by cells in the monocyte lineage, by circulating macrophages, and by tissue macrophages.
Tumor necrosis factor ligand superfamily member 9 also known as 4-1BB ligand or 4-1BBL or CD137L is a protein that in humans is encoded by the TNFSF9 gene.
Protein L was first isolated from the surface of bacterial species Peptostreptococcus magnus and was found to bind immunoglobulins through L chain interaction, from which the name was suggested. It consists of 719 amino acid residues. The molecular weight of protein L purified from the cell walls of Peptostreptoccus magnus was first estimated as 95kD by SDS-PAGE in the presence of reducing agent 2-mercaptoethanol, while the molecular weight was determined to 76kD by gel chromatography in the presence of 6 M guanidine HCl. Protein L does not contain any interchain disulfide loops, nor does it consist of disulfide-linked subunits. It is an acidic molecule with a pI of 4.0. Unlike protein A and protein G, which bind to the Fc region of immunoglobulins (antibodies), protein L binds antibodies through light chain interactions. Since no part of the heavy chain is involved in the binding interaction, Protein L binds a wider range of antibody classes than protein A or G. Protein L binds to representatives of all antibody classes, including IgG, IgM, IgA, IgE and IgD. Single chain variable fragments (scFv) and Fab fragments also bind to protein L.
Neutral and basic amino acid transport protein rBAT is a protein that in humans is encoded by the SLC3A1 gene.
CD151 molecule, also known as CD151, is a human gene.
Collagen alpha-3(IV) chain is a protein that in humans is encoded by the COL4A3 gene.
CD81 molecule, also known as CD81, is a protein which in humans is encoded by the CD81 gene. It is also known as 26 kDa cell surface protein, TAPA-1, and Tetraspanin-28 (Tspan-28).
CD48 antigen also known as B-lymphocyte activation marker (BLAST-1) or signaling lymphocytic activation molecule 2 (SLAMF2) is a protein that in humans is encoded by the CD48 gene.
Y+L amino acid transporter 1 is a protein that in humans is encoded by the SLC7A7 gene.
Large neutral amino acids transporter small subunit 2 is a protein that in humans is encoded by the SLC7A8 gene.
Sialic acid-binding Ig-like lectin 10 is a protein that in humans is encoded by the SIGLEC10 gene. Siglec-G is often referred to as the murine paralog of human Siglec-10
Large neutral amino acids transporter small subunit 1, also known as 4F2 light chain, or CD98 light chain is a protein that in humans is encoded by the SLC7A5 gene.
Y+L amino acid transporter 2, also known as cationic amino acid transporter, y+ system, is a protein that in humans is encoded by the SLC7A6 gene.
Asc-type amino acid transporter 1 (Asc-1) is a protein that in humans is encoded by the SLC7A10 gene.
