33
Cells are based of different compartments
2
Antigen presentation for what reason?
3
Activation of T-Cells
Proliferation is intracellular located and are not accessible for antibodies
Virus and somebacteria andparasites
Which cells are necessary for antigen presentation?
4
Key player of the adaptive immunity
T-Cells(out of the thymus)
T-cells are necessary for the control of intracellularpathogens and are responsible for the activation of B-Cellsagainst most antigens (exception: Superantigens)
Which cells are necessary for antigen presentation?
5
Cell based reaction between T-Lymphocyts and antigen presenting cells (cells which recognize the antigen, which is presented on the T-cells)
In both cases recognize T-cells the target cells based on peptide fragments of different proteins (f.e. virus- or bacterial components).
T-helper-cells (CD4+-T-cells)Cytotoxic cells (CD8+-T-cells)
HLA or MHC
6
„Haupthistokompatibilitätskomplex (HLA)“or
Majorhistocompatibility complex (MHC)
Are membrane bound glycoproteins, which present peptides as antigen to the T-cell.
MHC-Gens are important for the compatibility of tissue transplants, because many tight-knit polymorph Gens are responsible for the Histocompatibility.
MHCI and MHCII
7
T-cells recognize peptide fragments, which are from an extrinsic antigen, only if they are bound to an MHC-molecule.
Es gibt zwei Klassen von MHC-Molekülen:
MHC I-moleculeMHC II-molecule
Important differenses: -> Home of the peptide, which „capture“ the MHC-molecules and transport them to the cell membrane.
MHC I molecule expressed by nucleolare cellsMHC II molecule only expressend from antigen-presenting cells
Overview on antigen-presenting cells and their function
Pathogens and their products are located in the cytoplasm or in cell vesicles.
Characterisation of antigen-presenting molecules MHC
1.Step: Antigen uptake- and processing
MHC I molecules are out of the cytosol
2. Step: Stimulation of T-cells with antigen-presenting cells
Molecular structure of MHC I
Conserved amino acids coordinate the binding of peptides to MHCI
MHC I-T-cell complex
MHC II molecules, which are presented on the surface of APC are from extracellular antigen
Molecular structure of MHC II
Binding of peptides to MHC II
MHC II-T-Zellkomplex
MHC and the peptid have to be bound specific from the T-cells for activation
auf Chromosom 6
auf Chromosom 17
Genome organization of MHC by human and mice
Polygenie
Polymorphism and polygene improved the MHC-Variability
Codominate Expressionvon MHC Allelen!
Variability of allele is concentrated on the peptide binding region of MHC
One specific MHC molecule is able to bind many different peptides
Ala A
Cys C
Asp D
Glu E
Phe F
Gly G
His HIle ILys KLeu LMet MAsn N
Pro P
Gln Q
Arg R
Ser SThr TVal VTrp WTyr Y
Variability of MHC Allele in Humans
Rejection of organs: different situations are possible!
Strategies of pathogens to invade the immune system by blocking the antigen presentation
Presentation of MHC I with peptides
Transport of MHC I peptide complex to the cell surface
cellular synthesis of MHC II molecules
Presentation of MHC II with peptides
Cross-Presentation
Summary
