A T-cell precursors migrate from the bone marrow to thymus

1. A T-cell precursors migrate from the bone marrow to thymus

2. Shaping the T-cell repertoire. Positive and negative selection Thymus

3. Few TCR reacts with the MHC (about 2%) most T-cells die of neglect. ( no survival signals) α-chain rearrangement can continue until the assembly of a functional αβ receptor has been assembled.

4. Selection of developing T-cells in the thymus Bare lymphocyte syndrome MHCI vagy MHCII deficiency Lack of CD8+ or CD4+ cells Role of co-receptors in the development of single + T-cells

5. DC Macrophage in medulla of Thymus. Special transcription factor expressed… AIRE. Tissue spec. Antigens expressed AIRE mutaton: Autoimmune polyendocrinopathy -candidiasis-ectodermal dystrophy

6. Multiple stages of T-cell development in the thymus

7. Dendritic cells take up antigen in the tissues, migrate to peripheral lymphoid organs, and present foreign antigens to naive T cells.

8. Changes in the function of dendritic cells following Activation, migration to the regional lymph node, maturation Uptake of antigen, maturation Differentiation/maturation Antigen prezentation Red: lizozyme green: MHCII

9. A naive cells meet dendritikuc cells in the secondary lymphoid organs

10. (review) Phases of T cell response

11. The site of interaction between T cell and APC is called The imunological synapse

12. Clustering of the T-cell receptor and a co-receptor initiates signaling within the T cell.

13. TCR signaling (review)

14. T CELL ACTIVATION

15. CHARACTERISTICS OF T-CELL ANTIGEN RECOGNITION ACCESSORY CELL B-CELL T-CELL ANTIGEN BINDING NO INTERACTION T-CELL ACTIVATION Antigen receptor • The TCR is not able to interact directlywith soluble or cell-bound antigen • T-cell activation can be induced by antigen in the presence of acessory cells, only • 3. T-cells recognize virus-infected cells V C a/b

16. T CELL RECEPTOR MEDIATED SIGNALING εδεγ αβ ζζ Multisubunit Immune Recognition Receptors MIRR ITAM Immunoreceptor Tyrosine-based Activation Motif ACTIVATION

17. (review) Phases of T cell response

18. BCR signaling (review)

19. TCR signaling (review)

20. Intracellular (cytoplasmatic) Ca2+ concentration increase The intracytoplasmatic Ca2+ increase can be monitored by fluorescent indicator dye. The intensity or the specificity of fluorescence increase paralelly with the Ca2+ concentration.

21. Kinetic measurements connected to signaling (1.) Homogenous population – single cell property measured one after the other - timing Detected in homogenous population – measured cell by cell Detected in single cell Indicator–detection of intracellular Ca2+signal fluorescent Ca2+ indicatorsFluo-3orIndo-1

22. Kinetic measurements connected to signaling (2.) Fluo-3 AM – excitable by blue light Indo-1 AM – excitable by UV light These indicator dyes connected with apolar groups (e.g. acetoxy-methylester: AM) – go across the cell membrane. In the cell, estherases cleveage these groups - the fluorochrome became polar – catched in the cell for example – ic Ca2+signal in a single cell antigenpresentation by B cell to T cell (click)

23. THE IMMUNOLOGICAL SYNAPSE

24. APC T CELL

25. THE INTERACTION OF T CELLS AND ANTIGEN PRESENTING CELLS 1 2 3 4 5 6 7 8 interaction recognition stabilization separation Negulescu P.A. et. al. Immunity 4: 421-430, 1996

27. T-cells need two signals!!!! The role of co-stimulation

28. Signal 1 antigen & antigenreceptor T APC ACTIVATION Signal 2 B7 family members (CD80 & CD86) CD28 Antigen presentation - T cells are co-stimulated Costimulatory molecules are expressed by professional APC including dendritic cells, monocytes, macrophages, and B cells, but not by cells that have no immunoregulatory functions such as muscle, nerves, hepatocytes, epithelial cells etc.

29. ROLE OF CO-STIMULATION IN THE ACTIVATION OF HELPER T CELLS CD40L CD28 CD40 B7 B7 APC APC APC NORMAL TISSUE CELLS DO NOT EXPRESS CD40 OR B7 CO-STIMULATORY MOLECULES

30. Antigen 1 IL-2 IL-2 IL-2R IL-2R Mechanism of co-stimulation in T cells Resting T cells Signal 1 NFAT binds to the promoter of of the a chain gene of the IL-2 receptor. The a chain converts the IL-2R to a high affinity form Express a low affinity IL-2 receptor-  and  chains and produce no IL-2

31. Costimulation Antigen 2 1 IL-2 IL-2R Mechanism of co-stimulation in T cells Signal 2 Activates AP-1 and NFk-B to increase IL-2 gene transcription by 3 fold Stabilises and thus increases the half-life of IL-2 mRNA by 20-30 fold IL-2 production increased by 100 fold overall Immunosuppressive drugs illustrate the importance of IL-2 in immune responses Cyclosporin & FK506 inhibit IL-2 by disrupting TcR signalling Rapamycin inhibits IL-2R signalling

32. INITIATION OF T CELL PROLIFERATION IL-2R IL-2 IL-2Rα IL-2R low affinity recognition IL-2R high affinity transferrin costimulation insulin IL-1 IL-2 IL-2 AUTOCRINE GROTH FACTOR PROLIFERATION

33. CO-STIMULATION IS ESSENTIAL FOR PRIMING OF NAIVE T LYMPHOCYTES The antigen-specific and the co-stimulatory signals have to be induced in concert to induce T lymphocyte activation The antigen-specific and co-stimulatory signals can be delivered simultaneously by professional antigen presenting cells, only The antigen-specific and the co-stimulatory singnals has to be delivered by the same professional antigen presenting cell

34. T CELLS REQUIRE TWO SIGNALS TO GET ACTIVATED APC not presenting antigen Activated APC Resting APC B7 B7 CD4 CD4 CD4 CD28 CD28 CD28 21 1 2 T-cell activation T-cell anergy No effect ANTIGEN SPECIFIC ACTIVATION, ANERGY OR NEGLECTION

35. Naïve T cell Antigen 1 IL-2 IL-2R Epithelial cell Anergy Signal 1only The T cell is unable to produce IL-2 and therefore is unable to proliferate or be clonally selected. Unlike immunosupressive drugs that inhibit ALL specificities of T cell, Signal 1 in the absence of signal 2 causes T cell unresponsiveness to a specific antigen Self peptide epitopes presented by a non-classical APC e.g. an epithelial cell

36. Dendritic cells are sensors, gatekeepers and messengers Activation induces a phenotype essential for the initiation of the adaptive immune response

37. ACTIVATION AND MIGRATION OF DENDRITIC CELLS Effector and memory T cells LYMPH Activated DC Inflammation Pathogen Naive T cells ANTIGEN BLOOD Tissue DC TISSUE LYMPH NODE TISSUE INTERACTION OG DC AND T CELL T CELL ACTIVATION

38. DENDRITIC CELL T - LYMPHOCITE INTERACTION IN THE LYMPHOID ORGANS Activated dendritic cells in the lymphatic tissues act as antigen presenting cells Tight contact with specific T cells

39. DENDRITIC CELL-T CELL INTERACTIONS IN THE T-CELL AREAS OF LYMPH NODES NUCLEUS T CELL T CELL CYTOPLASM

40. Cell-surface molecules of the immunoglobulin superfamily initiate lymphocyte adhesion to professional antigen-presenting cells B. Transient interactions are stabilized by Ag-binding A. Initial contact A

41. Capture of an Ag-Specific T Cell by an Ag-Bearing DC Rapid DC Migration in the Subcapsular Space Bone-marrow derived DCs (green)or (50 µM Cell Tracker Blue, blue) were injected into the footpad of a C57BL/6 mouse, followed 18 hours later by intravenous injection of freshly isolated T cells ( red) Bone-marrow derived DCs (yellow) were pulsed with 1 µM Ova 4 peptide and 10 µM Ova for 1 hour at 37oC, then injected into the footpad of a C57BL/6 recipient. This was followed 6 hours later by i.v. co-injection of CD8+ T cells (green) and CD4+ T cells (red). Huang et al Immunity 2004

42. The stages of activation of CD4 T cells.

43. Different cytokine environments drive the differentiation of CD4 T cells that make different cytokines and have different functions.

44. Responses to Mycobacterium leprae are sharply differentiated in tuberculoid and lepromatous leprosy.

46. Granulomas develop when intracellular pathogens resist elimination Long term persistance of infectious agent in a separated envitonment

47. The three types of effector T cell produce distinct sets of effector molecules.

48. TH1 CD4 cells activate macrophages to become highly microbicidal. TH2 cells stimulate the proliferation and differentiation of naive B cells.