免疫03-antigen.ppt

第二章 抗原 Antigen（Ag） Antigen 1. Concept 2. Immunogenicity and specificity 3. Requirements for immunogenicity 4. Types of antigens 5. Superantigen and adjuvants Concept 1. Antigen (Ag) – the substances that are recognized by TCR/BCR or antibody and induce a specific immune response. 2.Properties of Ag -⑴immunogenicity -⑵antigenicity or immunoreactivity (react with the products of a specific immune response) 3. Immunogen -A substance that induces a specific immune response. Complete Ags：have the properties of immunogenicity and immunoreactivity. Hapten（半抗原）：have the property of immunoreactivity but not immunogenicity . - A substance that is non-immunogenic but which can react with the products of a specific immune response. Haptens are small molecules which could never induce an immune response when administered by themselves but which can when coupled to a carrier molecule. hapten + carrier → complete Ag 5. Tolerogen, allergen Tolerogen: an antigen that induces a state of specific immunological unresponsiveness Allergen: a substance capable of inducing allergy or specific hypersensitivity. pollens, dust, drugs, and foods… Foreignness and specificity Ⅰ. Foreignness - The immune system normally discriminates between self and non-self such that only foreign molecules are immunogenic. Ⅱ. specificity 1. epitope (antigenic determinant ) 抗原决定簇（基），表位 - the portion of the antigen that binds specifically with the binding site of an antibody or a receptor on a lymphocyte. - the size of an epitope is approximately equivalent to 5-15 amino acids. 2. the types of epitope ▲conformational epitope: Some epitopes form only when the critical residues are brought together in space through folding of the polypeptide or polysaccharide chain into its normal three-dimensional conformation. ▲sequential epitope: All of the amino acid or sugar residues that form a given epitope are posi