BIO 226T - Lecture 17 & 18 Study Questions

BIO 226T - Lecture 17 & 18 Study Questions - Lecture 17...

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1. Immunogen – substance capable of inducing an immune response ; such a substance is said to be immunogenic . [All immunogens are antigens, but some antigens (e.g. haptens) are not immunogens.] Antigen – any substance (usually foreign) that binds specifically to an antibody or a T- cell receptor (TCR) ; such a substance is said to be antigenic . Hapten low molecular weight compound which is not immunogenic , but which is antigenic ; can become immunogenic when covalently bound to a carrier protein . [Examples of haptens: drugs, hormones, catechol in plant oil that causes poison ivy] Epitope (antigenic determinant) – the specific site on an antigen that is recognized and bound by a particular immunoglobulin or TCR Valence – number of antigenic determinants [epitopes] on an antigen or the number of antigen-binding sites possessed by an antibody molecule [Examples: multivalent antigen (bacterium on p. 328); valence of IgM = 10, IgG = 2] 2. Properties of immunogens that influence their immunogenicity: Foreignness – molecules foreign to the host are immunogenic (immune system normally discriminates between self and non-self) Molecular size most potent immunogens are proteins with molec wt > 100,000; small molecules (i.e. amino acids, monosaccharides) with molec wt < 10,000 are not immunogenic; extremely small molecules with molec wt < 1000 can induce an immune response only when covalently linked to a larger carrier protein Chemical complexity – synthetic polymers consisting of single amino acids or sugars are not immunogenic; polymers of sufficient size (containing 2 or more different amino acids) are immunogenic; adding aromatic amino acids (i.e. tyrosine, phenylalanine) enhances the immunogenicity of synthetic polymers; three dimensional shape is important, and all four levels of protein organization affect immunogenicity of proteins Chemical composition – proteins function as the most potent immunogens, with polysaccharides ranking second; lipids and nucleic acids are not immunogenic unless complexed with proteins to form lipoprotein or nucleoprotein complexes Dosage, route, and timing of antigen administration – optimal dosage and route of administration which will give a peak immune response is determined empirically (by
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This note was uploaded on 03/19/2008 for the course BIO 226T taught by Professor Field during the Fall '06 term at University of Texas at Austin.

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BIO 226T - Lecture 17 &amp; 18 Study Questions - Lecture 17...

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