Cytokines

1. Cytokines Jennifer Nyland, PhD Office: Bldg#1, Room B10 Phone: 733-1586 Email: jnyland@uscmed.sc.edu

2. Teaching objectives • To highlight the major cytokines that are mediators of 1) innate immune response, 2) adaptive immune response, and 3) hematopoesis • To describe the families of cytokine receptors • To discuss the cytokine network

3. Cytokines • Non-Ab proteins acting as mediators between cells • Monokines: produced by mononuclear phagocytes • Lymphokines: produced by activated lymphocytes, especially Th cells • Interleukins: cytokines that act as mediators between leukocytes • IL and a number • Chemokines: small cytokines responsible for leukocyte migration

4. Cytokine network • Complex system of interactions between cytokines wherein one cytokine can: • Induce or suppress its own synthesis • Induce or suppress synthesis of other cytokines • Induce or suppress synthesis of cytokine receptors • Antagonize or synergize with other cytokines

5. Cytokine network • Complex interactions • Often cascades • Different cells can respond differently • Differential signal transduction • Differential receptor expression • Very flexible • Can protect or damage • Support angiogenesis vs inflammation

6. Properties of cytokines • Produced by cells involved in innate and adaptive immune response • Mediate and regulate immune responses • Secretion is limited • Not stored pre-formed • Synthesis initiated by gene transcription • mRNA is short lived • Produced as needed • Can be produced by many cell types and act on many cell types (pleotropic)

7. Properties of cytokines • Can have similar actions (redundant) • Can share receptors or receptor components • Defect in a unique component: little effect • Defect in shared component: profound effect • IL-2Rγ defect X-linked SCID • Genes encoding cytokines can produce variants through alternative splicing • Yield slightly different but biologically significant bioactivities

8. JAK JAK STAT STAT Cytokine receptors • Most are formed as heterodimers • Many can be grouped into families based on common structural features TRAF IRAK

9. Cytokine receptors: type 1 (IL-2 family) • Lack intrinsic protein Tyr kinase activity • Include IL-2, IL-4, IL-12, GM-CSF • 3 subsets based on common components • IL2Rγ, common β, gp130 • Ligand binding leads to R dimerization/trimers • Both homo- and heterodimers

10. Cytokine receptors- type 2 (IFN family) • Include IFN-γ and IL-10 • Conserved cysteines in extracellular domains • Tandem Ig-like domains in extracellular region • Intrinsic protein Tyr-kinase activity

11. Chemokine receptors • All chemokine Rs have seven transmembrane segments linked to GTP-binding proteins • Named based on the family of cytokines to which they bind: • CCR binds to CC chemokines • CXCR binds to CXC chemokines • Selectively expressed on particular lymphocyte populations

12. Summary of cytokine actions • Pleiotrophy • Redundancy • Synergism/antagonism • Cytokine cascade • Receptor transmodulation • Receptor trans-signaling

13. Categories of cytokines Mediators of the innate immune response

14. Mediators of innate immune response • TNF-α • IL-1 • IL-10 • IL-12 • Type 1 interferons (IFN-α, IFN-β) • IFN-γ • chemokines

15. Tumor necrosis factor (TNF-α) • Produced by activated macrophages • Most important mediator of acute inflammation in response to microbes (esp gram negative bacteria) • Mediates recruitment of neutrophils and macrophages to site of inflammation by inducing ICAM, etc on endothelial cells • Stimulates endothelial cells and macrophages to produce chemokines • Acts on hypothalamus to produce fever • Promotes production of acute phase proteins

16. Interleukin 1 (IL-1) • Produced by activated macrophages • Effects similar to TNF-α • Helps activate Ts

17. Interleukin 10 (IL-10) • Produced by activated macrophages and Th2 cells • Function in both innate and adaptive immune response • Inhibitory cytokine • Inhibits production of IFN-γ by Th1 cells • Shifts balance to Th2 • Inhibits cytokine production by activated macrophages • Inhibits expression of MHC class II and co-stimulatory molecules on macrophages

18. Interleukin 12 (IL-12) • Produced by activated macrophages and DCs • Stimulates production of IFN-γ • Induces differentiation of Th cells to Th1 • Enhances cytolytic functions of Ts and NK cells

19. Type 1 interferons (IFN-α, IFN-β) • Produced by macrophages and many cell types • Inhibit viral replication in cells • Increase expression of MHC class I • Activate NK cells

20. Interferon gamma (IFN-γ) • Produced by Th1 cells • Numerous function in both innate and adaptive immune response

21. Chemokines • Small cytokines • Produced by many leukocytes and other cell types • Large family of molecules (over 50) • Role: determine which cells cross epithelium and where they will go • Migration: Recruit leukocytes to sites of infection/lymphocyte trafficking • Activation: dual binding sites on chemokine • Chemotaxis: Chemotactic for leukocytes

22. Chemokines • Four families based on spacing of conserved cysteine • α-chemokines have CXC structure • β-chemokines have CC structure • Individual chemokines often bind more than one receptor and vice versa

23. Categories of cytokines Mediators of the adaptive immune response

24. Mediators of adaptive immune response • IL-2 • IL-4 • IL-5 • TGF-β • IL-10 (see previous) • IFN-γ (see previous)

25. Interleukin 2 (IL-2) • Produced by Th • Main grown factor for Ts • B cell growth factor • NK activator • Monocyte activator

26. Autocrine role of IL-2 • T activation • IL-2 secretion • IL-2R expression • Cell division • Receptor decay

27. Interleukin 4 (IL-4) • Produced by macrophages and Th2 cells • Stimulates development of Th2 from naïve Th • Promotes growth of differentiated Th2 cells • Stimulates Ig class switching to IgE isotype

28. Interleukin 5 (IL-5) • Produced by Th2 cells • Promotes growth and differentiation of eosinophils • Activates mature eosinophils • Promotes B cell differentiation

29. Transforming growth factor (TGF-β) • Produced by Ts, macrophages, and other cell types • Inhibits proliferation of Ts • Inhibits activation of macrophages • Acts on PMNs and endothelial cells to block pro-inflammatory cytokine effects

30. Categories of cytokines Stimulators of hematopoesis

31. Stimulators of hematopoesis • GM-CSF • M-CSF • G-CSF

32. Granulocyte-macrophage colony stimulating factor (GM-CSF) • Promotes differentiation of bone marrow progenitors • Survival and growth factor for hematopoetic progenitor cells • Growth factor for endothelial cells, T cells, and others • Produced by T cells, macrophages, fibroblasts, and endothelial cells

33. Macrophage colony stimulating factor (M-CSF) • Promotes growth and differentiation of monocytes and macrophages • Complex protein • Produced as integral cell surface or secreted protein • Produced by many cell types including lymphocytes, monocytes, epithelial cells

34. Granulocyte colony stimulating factor (G-CSF) • Promotes production of PMNs • Synergizes with IL-3 to stimulate proliferation and migration of endothelial cells • Also know as pluripoietin

35. Categories of cytokines IL-17

36. Interleukin 17 (IL-17) • Proinflammatory cytokine, approx 150aa • 6 member family • Share sequence homology • Different tissue expression patterns • Produced by Th17 cells • Overproduction associated with autoimmune disease including MS, RA, IBDS

37. Cytokine network Beyond the immune cell effect

39. Cytokine network

40. Cytokine network

41. Cytokine network