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Antigen recognition in adaptive immunity. Mechanism of diversity of antigen receptors Maturation and selection of B lymphocytes Maturation and selection of T lymphocytes. Cells display several types of receptor and each of them is specific for a certain ligand.
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Antigen recognition in adaptive immunity Mechanism of diversity of antigen receptors Maturation and selection of B lymphocytes Maturation and selection of T lymphocytes
Cells display several types of receptor and each of them is specific for a certain ligand Cells within one clone display only one type of receptor specific for a certain ligand
Antigen receptors on lymphocytes B cell T cell Antigens: proteins, polysaccharides, lipids, nucleic acids, small molecules Conformational and linear epitops Complex of peptide-MHC molecule on an APC Linear epitops
N N N N C C C C
CDR1 CDR1 CDR2 CDR2 CDR3 CDR3 k l a (a1 a2) g (g1 g2 g3 g4) d e m VH VH VL VL CL CL Isotype IgA(1,2) IgG(1,2,3,4) V (variable) region VLi VH IgD CH CH IgE C (constant) region CL i CH IgM
Antibodies • structure • function
T-cellreceptor for antigen (TCR) structure
The Nobel Prize in Physiology or Medicine 1987 "for his discovery of the genetic principle for generation of antibody diversity" Susumu Tonegawa
54 ~100 67 27 Mechanisms of creation of antigen receptor diversity 61 4
Every day 109 lymphocytes with 107 variousspecificities are generated (young)
1. TCR gene recombination a. eliminates auto-reactive lymphocytes 2. Negative selection b. proteins, polysaccharides, lipids 3. TCR recognizes c. aandb,organddchains 4. Immunoglobulin gene recombination d. peptides within MHC molecule 5. TCR consists of e. constant region of heavy chains 6. Antibody has f. variable regions of heavy and light chains 7. Different isotypes have the same g. occurs only in thymus 8. Positive selection h. provides antibody diversity 9. Antibody can recognize i. two identical heavy and two identical light chains 10. Receptors of different clones of B cells have different j. enables survival of useful lymphocytes g a d h c i e j b f 1.____ 2.____ 3.____ 4.____ 5.____ 6.____ 7.____ 8.____ 9.____ 10.____