Transcript Document
Immune molecules Section 3 Chapter 1 properties of antigen immunogen Any substance capable of inducing an immune response. Antigen (Ag) substances that can induce an immune response and are recognized by a particular immunoglobulin or TCR, and so can serve as the target of an immune response. 2 important properties of Ag ---the ability for inducing an IR, including induce production of antibody and effector T cell Combine specifically Immunogenicity antigen ↓ IS ↓induce IR ↓ products of IR (Ab/effector T cells) Antigenicity/immunoreactivity ---the ability to combine specifically with the Ab or effector T cell induced by its own →immunogenicity →antigenicity Complete antigen & hapten A.Complete antigen ---Substances that have both immunogenicity and immunoreactivity(antigenicity) B.Hapten ---Substances that have immunoreactivity , but lack of immunogenicity (二硝基苯) combine with • • Hapten couple(偶联) to protein or other carriers to form complete antigen • hapten+carrier = complete antigen Chapter 2 characteristics of Ag specificity most of the immunogens encounterd in nature are complex assemblages made up of several different types molecules, not all of which are antigenic epitope the specific site to which a particular immunoglobulin or TCR binds antigenic determinant (AD) epitope Definition the specific site to which a particular immunoglobulin or TCR binds AD Ag B 抗原 antigen T Ag antigen Ag Specificity of antigen 多 价 AD 抗 原 多 价 抗 原 induce specificity of immunogenicity AD specificity of immunoreactivity Specificity of antigen Classification of epitope B cell epitopes • Linear epitope • Conformational epitope • T cell epitopes B cell epitope the regions that are recognized by immunoglobulins • linear epitopes • Conformational epitopes 构像表位和线性表位 T cell epitope • Proteinaceous Ag degraded into peptides • Some of peptides associate with an MHC protein • Peptide-MHC complex are presented on the APC surface • TCR recognizes peptide-MHC complex Macrophages Take Up Antigen Into Vesicles and Present Peptide Fragments From Proteins in MHC-II CD4+Th细胞 外源性抗原加工、处理和呈递示意图 Common Ag and cross reaction Some Ag usually strip multi-Ag epitope and can react with Ab or activate lymphocyts inducing • By themselves • By other inducing Ag 1 Ab 1 Ab 2 Ag 2 Common Ag Different Ag which contain sameness or similitude Ag epitope cross reaction Ab or activate lymphocyte react with sameness or similitude Ag epitope in different Ag Ag 1 Ab 1 Ab 2 Ag 2 （一）抗原的异质性与共同表位 Common Ag and cross reaction Ag1 Ag2 Foreignness • Only molecules that are foreign to the host are immunogenic • Immune system can recognize self and non-self Chapter 3 factors influencing immunogenicity Important factors • Foreigness(异物性) • Physicochemical characteristics • Host • Mode of contact Foreigness Non-self substances: do not contact sufficiently with immune cells during embryonic period Self tissue: tolerance Physicochemical properties of Ag Chemical property Molecule size Molecule Complexity conformation and accessibility （分子构象和易接近性） Chemical property • Proteins are the most effective immunogens • Nucleic acids and most lipids are antigenic but not immunogenic Hapten Molecular size • Molecular weights greater than 100,000 • Most other species smaller than 10,000 usually are not immunogenic A few substances with molecular weights below 1,000 can induce immune responses when bound to a larger, host-derived macromolecule. Molecular complexity • Homopolymers of a single amino acid may be poor immunogens • Copolymers of two or more are often quite active conformation and accessibility Immunogenicity +++ ± +++ Effect of host • The ability to respond to a particular immunogen is genetically predetermined Genetic characteristics of the host Age, sex, and state of health Mode of contact • Dosage • Route intracutaneous subcutaneous intramuscular intravenous oral Chapter 4 classification of Ag TD-Ag and TI-Ag TD-Ag • Most protein Ag require Ag-specific T cell help to generate an Ab response • The immune response to most Ag depend on both T cells and B cells TI-Ag Some Ag do not require the presence of helper T cells Classification based on relationship with host Heterophilic Ag • Forssman Ag • A kind of common Ag, • Exists in human, animals and microorganism • Related to some diseases rheumatic fever: • 2 weeks after infection • fever, migratory polyarthritis, carditis • immunologic cross-reaction between bacterial Ag and human heart and joint tissue • Can be prevented by treatment of infection within 8 days Bacteria induced producing Ab Ab bind epitope of bacteria Bacteria were eliminated Ab bind epitope of host tissue Xenogenic Ag The Ag come from different genus and generic The important xenogenic Ag: • Pathogenic microorganism • Plant protein • Animal serum • Heterogeneity organ implant Animal serum • • • • The serum come from animal Contain Ab Can treat or prevent disease May act as an immunogen Allogenic Ag The specific Ag exists in different individual of same genus • ABO red cell blood type Ag • Rh Ag system • HLA Autoantigen • Oneself component can induce body to self immune response enshrounded Ag isolation Ag self-Ag occur change or decorated Chapter 5 non-specific stimulators Super Ag (SAg) • Has the capability of activating 1%-10% of peripheral T cells • Exposure to a SAg can lead to massive T cell activation Adjuvant The response to an immunogen mixed with adjuvants can often be enhanced