Two categories of immune response. immune response. infection. (adaptive) Later immune response. immune response

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1 Ivana FELLNEROVÁ mob

2 Basic immunogenetic terminology innate and adaptive immunity specificity and polymorphism immunoglobuline gene superfamily immunogenetics MHC glykoproteins structure, function gene coding MHC molecules (HLA) Imunoglobulins, BCR, TCR structure, polymorphisms B-cell receptor development T-cell receptor development gene rearrangement, allelic exclusion

3 Two categories of immune response NONSPECIFIC (innate) immune response SPECIFIC (adaptive) immune response infection hours days 5 7 Initial defense against infection Later immune response [consists of activation of lymphocytes]

4 First line defense against many common microorganisms Distinguishes between the kind of carbohydrates that are produced by mammalian cells and those produced by bacteria.

5 Two categories of immune response SPECIFIC NONSPECIFIC (adaptive) Recognize a (innate) response specific immune foreign substanceimmune response [peptide] and selectively react to it. Recognize structure shared by groups Is mediated lymphocytes: of by hours related microorganisms ction infe Binfection cells: 0 6 by [carbohydrates produced bacteria recognize extracellular substance days 5 7 but no by mammalian cell] secrete antibody Mediated PHYSICAL and CHEMICAL BARIERS T cells:byinitial cell mediate defense immunity Later immune response against infection [mediated by T and B [macrophages, lymphocytes] recognize intracellular substance [skin, epithelia cells and secretes], LEUKOCYTES bound to self MHC molecule [complement proteins, cytokines] neutrophils, basophils], MEDIATORS

6 COMPONENTS CHARACTERISTICS Phagocytes [macrophages, neutrophiles] Natural killer cells Complement proteins Skin, mucosal epithelia Antimicrobial chemicals Recognize structures shared by groups of related microbes NO memory Diversity limited, germ line encoded Responds immediately Lymphocytes: T cell, B cell Antibodies Lymphocytes in epithelia, Antibod. secreted at epithelial surface Recognize specifically microbial or nonmicrobial protein antigens MEMORY Diversity extremely high Response develops later

7 TOLERANCE SELF [own], regular cells and molecules IMMUNE SURVALIANCE OWN dead, damaged or abnormal cell and molecules Immune system can recognize: Foreign [non-self] substance Protection against potential pathogens [disease-causing invaders] DEFENSE

8 The key feature of the adaptive immune system is The immune system is able distinguish between antigens or small parts of macromolecular antigens

9 Fine specificity is attributed to Those may bind to one molecule but not to another with only minor structural differences from the first

10 Unique specificity of antigen receptors and the ability to react selectively against a very broad range of foreign antigens is the result of extensive (Greek: poly =many, morphe =shape, structure) Polymorphism means: Existence of two or more alternative forms or variants of expressed proteins in a population

11 A broad repertoir of immune molecules is the result of: POLYMORPHIC GENES ES Alternative forms or variants are present in different members of the population [common variants are called alleles] NONPOLYMORPHIC GENES Genes represented by only one normal nuclei acid sequence in all members of a species

12 Polymorphic immune molecules belong to large family of proteins that contain a globular structure motif - Ig domain originally described in antibodies. This group of proteins is called:

13 Ig domain: A three dimensional globular structural motif found in many proteins in the immune system About 110 aminoacid residues in length The principal elements of domain are two opposedβplated sheets stabilized with disulfide bonds (β barrel)

14 There are about of immunoglobulin superfamily Recognition and regulation molecules: Ig, BCR, TCR, MHC molecules, CD2, CD3, CD4, CD8 molecules, Fc receptors Adhesion molecules : ICAM-1, ICAM-2, VCAM-1, PECAM-1 Receptors for PDGFR (= platelet growth factor)

15 IMMUNOGLOBULINs [ antibodies ] membrane glykoproteins (members of the immunoglobulin superfamily) Membrane receptor of B lymphocyte Membrane Receptor of T lymphocyte

16 Genes that encode on cell surface molecules are part of Appear to be evolutionary related genes Members of a family share a certain degree of sequence homology Are likely derived from a common precursor gene

17 The study of the GENETIC ASPECTS of the immune response: Immune response genes [ Ig gene superfamily] HLA antigens and their association with disease Generation of antibody diversity

18 ? ajor istocompatibility omplex Cluster of genes located on the short arm of chromosome 6 Highly polymorphic gene encoding membrane MHC glycoproteins MHC in humans is called HLA complex (= Human Leukocyte Antigens) WHERE? MHC [ HLA] molecules are found in all nuclear cells in humans 2 categories of MHC gene products in humans Class I MHC glykoproteins Class II MHC glykoproteins

19 Primary immunology function of binding to a peptide fragment derived from antigenic protein presenting a peptide fragment on the cell surface for recognition by the T cell receptor

20 APC (Antigen presenting cell) mediate immune response Cytokine release Complex MHC-antigen T cell T cell T cell T T cell T cell cell T cell ANTIGEN antigen processing antigen presentation T cell stimulation T cell proliferation

21 T lymphocyte T cell receptor PEPTIDE MHC protein antigen presenting cell

22 Class I glycoproteins Class II glycoproteins Dendritic cell macrophages Expressed on the surface of all nucleated cells ONLY at antigen presenting cells - APC(phagocytes, dendritic cells)

23 GLYCOPROTEINS GLYCOPROTEINS Bind peptides derived from cytosolic proteins Bind peptides derived from phagosome or endosome Bind peptides endogenously synthesized by cells [pathological or viral protein] Bind exogenous ous peptides derived from phagocyted proteins [ mostly bacterial proteins] Are recognized by cytotoxic T lymph phocyt ocytes es, c [ CD8+ T cell ] Are recognized by helper T lymph phocyt ocytes h [ CD4+ T cell]

24 Class I MHC Polymorphicαchain contains 3 domains (α 1 α 2 α 3 ) Nonpolymorphicβ 2 microglobulin 8-10 aminoacids Class II MHC Polymorphic α chain (domainsα 1 α 2 ) Polymorphic β chain (domainsβ 1 β 2 ) Up to 30 aminoacids α 2 α 1 α 1 β 1 α 3 β 2 Peptide binding cleft α 2 β 2 Nuclear cell Antigen presenting cell

25 Handle intrinsic peptide antigens Present antigens to cytotoxic T cells

26 Nuclear cell viral proteins mutated proteins (tumor cells)

27 Nuclear cell Komplex MHC-antigen T c cell (cytotoxic) viral proteins mutated proteins (tumor cells) T cell cytotoxic (CD 8 + T cell)

28 T c cell (cytotoxic) viral proteins mutated proteins (tumor cells) T cell cytotoxic (CD 8 + T cell)

29 The class I MHC pathway of antigen presentation Production of proteins In cytosol: 1.Viral proteins 2.Protein antigen of digested microbe transported to cytosol 3. Neoplastic protein Proteolytic degradation of proteins by proteasome (a large proteolytic protease) in cytosol Transport of peptides from cytosol to ER (by TAP-transporter associated with antigen processing) Assembly of peptide -class I complex (in ER) Peptide class I complex is transported through the Golgi apparatus to the cell surface And presented to the CD8+ T cells

30 Handle extrinsic peptide antigens Present antigens to helper T cells

31 APC

32 APC Complex MHC-antigen T H cell (helper) T cell helper (CD 4 + T cell)

33 APC Complex MHC-antigen T H cell (helper) B cell

34 Several steps of antigen presentation to CD 4+ T cells I i = invariant chain which protects MHC class II from binding to protein MIIC = MHC class II compartment

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38 Killing the cell CD8+ nuclear cell CD8+ CD8+ CD8+ CD8+ CD8+ CD8+ T c lymphocytes cytotoxic Stimulation of phagocythosis CD4+ CD4+ CD4+ CD4+ CD4+ CD4+ APC macrophages, dendritic cell Antibody production B CD4+ T h lymphocytes helper

39 Genes encoding MHC (HLA) glycoproteins are the most IN MAMMALIAN GENOME Located on the short arm of chromosome 6 in humans

40 MHC II locus MHC I locus MHC III (loci DP, DQ, DR) locus (loci A, B, C) Complement DP DQ DR proteins B C A and cytokines α >20 β>107 α>25 β>56 α>3 β>439 > 563 > 176 > 309 There are many DNA variants [alleles] at each locus and hundreds of antigenic variants of MHC molecules [expressed MHC proteins]

41 Human MHC genes are highly polymorphic August 2000 (Nomenclature Committee for Factors of HLA system) Source: CH. A. Janeway & all.: IMMUNOBIOLOGY, the immune system in health and disease 5 th eddition, 2001 April 2007: Full list of HLA alleles HLA class I : HLA class II :

42 MHC class I and MHC Class II form the particular loci were distinguished using specific antibodies which could recognize polymorphic variants at the loci Using newer antibodies more and more variants of MHC genes will be found

43 Several sequences (genetic variants) can have the same LOCUS HLA-B GENETIC VARIANT (sequences) HLA-B*1301 HLA-B*1302 HLA-B*1303 HLA-B*1304 HLA-B*1305 HLA-B*1306 ANTIBODY USED for detection HLA-B13 Locus HLA-B*13 06 Two digits indicate the serological specificities Sequence number Variation of aminoacid sequences change the shape of the binding groove

44 Genes coded MHC class II molecules Genes coded complement proteins Genes coded proteasomes (proteins involved in antigen processing and presentation) Class I molecules Class I-like molecules Genes induced in response to cellular stress (heat shock proteins)

45 Only identical twins will inherit Exactly the same set of MHC molecules MHC molecules are encoded by huge numbers of allels It is unlikely that any two people will inherit exactly the same set The repertoire of MHC proteins vary from person to person

46 MHC molecules are involved in Foreign MHC molecules of a donor are recognized by the T cells of recipient DONOR Incompatibility RECEPIENT HLA-A1 HLA-A7 HLA-B12 HLA-B26 A7 B12!! A39 B18 HLA-A3 HLA-A39 HLA-B18 HLA-B26 B26 A1! A3 B26

47 Other highly polymorphic immune molecules: IMMUNOGLOBULINS [ antibodies ] Membrane receptor of B lymphocyte Membrane receptor of T lymphocyte A unique process during development and maturation allows for the generation of enormous diversity

48 Potential to create a huge number of different antibodies and membrane receptors protect a person against the large array of to which a person may be exposed

49 REPERTOIRE The whole range of antibodies in one person

50 Sequence at the variable region of an antibody is compatible to... Antigen which specifically binds to a particular antibody... the sequence at the epitope of a particular antigen Antibody [ receptor] specific to a particular antigen

51 VARIABLE REGION (antigen binding site ) LIGHT CHAIN Constant region HEAVY CHAIN Constant region α β B lymph phocyt ocyte T lymphocyte

52 Central lymphatic organs: bone marrow, thymus Periferal lymphatic organs Pre- B cell BCR- BCR+ B lymphocyte BCR++ Stem cell Positive selection CD4+ TCR+ immature B lymphocyte T h lymphocyt CD4+ TCR++ Positive/ negative selection Thymus CD4+ CD8+ TCR(+) CD8+ TCR+ core T c lymfocyt CD8+ TCR++

53 B-lymphocyte activation [ exposure to antigen ] Antibody secretion specificity Plasma cell PROLIFERATION Antigen-antibody binding

54 = immunoglobulins = gama - globulins Glycoproteins found in serum variable region Y-shape molecule made of two identical heavy chains and two identical light chains Constant region (C-terminal) Variable regions (N-terminal) form antigen binding sites which specifically bind particular antigens LIGHT CHAIN HEAVY CHAIN Constant region

55 B cell membrane [BCR] How do that differ? What is common? [ immunoglobulin ]

56 Stimulation by antigen ANTIBODY SECRETION Membrane IgG = Secreted IgG B lymphocyte

57 Stimulation by antigen ANTIBODY SECRETION Membrane IgG = B lymphocyte IgM secreted

58 Ig, BCR and TCR are encoded in the germline by a relatively small number of genes The generation of enormous diversity allows a unique process during development and maturation : and Genes encoding Ig, BCR and TCR are on chromosomes 2, 14, 22

59 GENES encoding Ig, BCR and TCR Chromosomes # 2, 14 and 22 Variable region Constant reagion B cell Ig (BCR) Heavy chain Ig (BCR) Light chain CHROMOSOME # 14 V D J C CHROMOSOMES # 2 (κ), 22 (λ) V J C Chromosomes contains regions V, D, J and C CHROMOSOME # 7 T cell TCR β chain TCR α chain V D J C CHROMOSOME # 14 V J C

60 Each region has many segments variability > 100 diversity ~ 50 joining 9 Gene encoding constant region V D J C D J rearrangement V D rearrangement splicing V D J rearranged DNA, which serves as a template for transcription and translation

61 HEAVY CHAIN LIGHT CHAIN Germline DNA D J joined rearanged DNA V D joined rearanged DNA Primary transkript RNA Somatic recombination Transcription mrna splicing Translation Polypeptide chain

62 Gene segment rearrangement happens on both homologue chromosomes at the same time STOP correct V-D-J-C sequence Rearrangement on the pair hom. chromosome is terminated

63 IMMUNOGLOBULINS TCR TOTAL DIVERSITY ~ ~ 10 18

64 Abbas A. K., Lichtman A. H. (2003) Cellular and molecular immunology Janeway Ch. A. a kol. (2001) Immunibiology Roitt I. M., Delves P. J. (2001) Essential immunology Nussbaum R. L. a kol. Genetics in medicine Hořejší V., Bartůňková J. (2002) Základy imunologie