Immunology for Surgeons : The Basics 101

1. Immunology for Surgeons:The Basics 101 Principles of Surgery Jeff Warren, MD, FRCSC October 19, 2010

2. Objectives • The Players -- T-cells and B-cells • Immunoglobulins • Antigen Recognition • Phagocytosis • Mediators and Complement • Immunization • Hypersensitivity Reactions • Transplant Immunology Basics

3. Immunology • Conceptually challenging • Complex series of reactions triggered by immunogens • Compartmentalize to simplify, but actual events at molecular and cellular level are “boundary-less” and only partially understood • More we learn the less we know

4. Introduction • Innate vs Adaptive immunity • Self vs non-self vs altered self • Three phases of immune response: • Cognitive phase • Activation phase • Effector phase • Primary and Secondary responses • Lymphoid organs: primary/secondary • Humoral and Cell-mediated responses

6. T-cells Thymus CD3+ CD4+ -- Helper and DTH CD8+ -- cytotoxic and suppressor NK Cells Non B-cell, non T-cell lymphocytes +IL-2 --> LAK cells B-cells Bursa fasicularis (birds) Fetal liver and bone marrow CD19+/CD20+ --> plasma cells --> Ab production APCs Lymphocytes

7. B-cell-->Plasma cell--> Ig production • IgA: secretory, dimer • IgG: most abundant, 2o response, opsonin, C’ binding • IgM: 1o repsonse, C’binding, pentamer • IgE: mast cells and basophils, Type I hypersensitivity • IgD: small quantities, ??

8. Immunoglobulin

9. Immunoglobulin -- Fab and Fc

10. Antigen Recognition • Immunogen: can stimulate immune response • Antigen: recognized by immune system • Immunogenicity: • Complexity: proteins > CHO > nucleic acids > lipids • Size: usually > 5000 Da • Foreigness: xenogeneic > allogeneic > syngeneic > autologous

12. MHC • HLA in humans on chromosome 6 • With Ag --> Self vs non-self vs altered self • Class I: A and B regions, on all nucleated cells and platelets, recognized CD8+ T-cells --> lysis • Class II: D region, on APCs, recognized CD4+ helper T-cells --> activation and proliferation of helper T-cells (--> cytokines), cytotoxic T-cells (--> lysis), and B-cells (--> plasma cells --> Ab) • Class III: Complement

13. MHC Class I and Class II

14. Antigen Presenting Cells (APC) • Capable of activating CD4+ T-cells • Recognition usually occurs in 2o lymphoid organs: spleen, lymph nodes, GALT, Peyer’s patches… • Monocyte and macrophage lineage: • Dendritic cells (skin) • Kupfer cells (liver) • Glial cells (CNS) • B-cell subset

15. Any nucleated cell APC

16. Ag Recognition …but not enough… need Co-Stimulatory Signal 2

18. T-cell receptor

19. Phagocytosis • Mononuclear (monocytes) vs polymorphonuclear (neutrophils) • Engulfed foreign particle --> phagosome + lysosome --> phagolysosome • Oxygen-dependent mechanisms: • Myeloperoxidase, superoxide anion, H2O2, singlet O2, OH- radicals • Oxygen-independent mechanisms: • Cationic proteins, lysozymes, proteinases

20. Phases of Phagocytosis

21. Complement • Component proteins mediators of inflammation and cell lysis • Numbered according to chronological discovery, not necessarily order of activity in cascade reactions • Traditionally divided into Classic, Alternative, and Lectin pathways • Small stimulus --> amplified effect • Initiated by Ag-Ab immune complexes and microbial products • C3a and C5a are chemotactic • Some components are anaphylatoxins --> mast cell degranulation, smooth muscle contraction, increased vascular permeability • End-product is C5b-8 MAC

22. Complicated!…

23. …simplified.

24. Cytokines • Greek -cyto, cell; and -kinos, movement • Large group of cell-signaling molecules: • proteins, glycoproteins, peptides • Grossly include interleukins, lymphokines, and chemokines; redundancy and pleitropism make this classification obsolete today.

25. Interleukins • IL-1: pro-inflammatory and wound healing; macrophages, neutrophils, fibroblasts, NK cells, endothelial cells, vascular smooth muscle; fever, vasodilation, hypotension, collagen deposition, T-and B-cell proliferation, IL-2 and IL-2R up-regulation • IL-2: “T-cell growth factor” in response to IL-1; NK cells and activated T-cells (auto- and para-crine); up regulates many other cytokines, namely TNF and CSF; deficiency --> SCID • IL-3: hematopoetic growth factor • IL-4: inhibits macrophages • IL-6: inhibits TNF • IL-8: neutrophil chemokine • IL-10: inhibits monocytes/macrophages and anti-inflammatory IL-4, 6, and 10 are “inhibitory” cytokines

26. IL-2

27. Tumor necrosis factor (TNF) • Hemmorhagic necrosis in methycholanthrine -induced sarcomas in mice • TNF-alpha: 1o monocytes/macrophages, but NK cells and neutrophils also • Stimulates neutrophils • Endothelial cells --> IL-1 • Procoagulant, increased vascular permeability • Catabolism and cachexia in malignant disease • Apoptotic mediator • Gram negative shock --> endotoxin --> TNF-alpha --> hypotension + DIC • TNF-ß: T- and B-cells • Wound healing, PG and collagen deposition • Cytolytic and cytostatic for many tumor cell lines

29. Interferons • Glycoproteins • Inhibit viral proliferation via signaling pathways and translation machinery inhibition • INF-alpha -- macrophages • INF-beta -- epithelial cells, fibroblasts, macrophages • INF-gamma -- T-cells and NK cells • Antiproliferative • Can induce differentiation • Stimulate or inhibit a variety of cells to release other cytokines

30. Chemokines • Low molecular weight cytokines that serve as chemoattractants • 4 cysteine molecules linke by disulfide bonds • C-C or C-X-C and their receptors • IL-8 is actually a chemokine that binds CXCR1 or CXCR2 on neutrophils • 100s of chemokines identified and the catalogue continues to grow!

33. Immunization • Active: injection of intact attenuated organism or component. Recipient mounts an immune response with the goal being memory • DPT, MMR, pneumovax, HepB, vaccine, polio vaccines • Passive: exogenous active component is given to recipient; immediate but temporary immunity • Antitoxins: C.tetani antitoxin • Immunoglobulin: IgG to immundeficient recipient • Specific immune globulin: RhoGAM (prevent sensitization to Rh Abs crossing placenta from Rh+ infant at delivery)

34. Who were these guys?… Dr. Albert Sabin Dr. Jonas Salk

35. Hypersensitivity Reactions • Type I: immediate hypersensitivity • IgE mediated --> mast cells and basophils • Anaphylaxis, hay fever, food allergy • Type II: cytotoxic reactions • IgG and/or IgM mediated; preformed Abs • ABO and Rh incompatibility, myasthenia gravis, Graves disease, ITP • Type III: immune complex mediated • Deposition of Ab-Ag complexes • PSGN, serum sickness, SLE, rheumatoid arthritis • Type IV: DTH • Previously sensitized CD4+ T-helper cells • Tuberculin skin test, contact dermatitis

36. Transplant Rejection • Hyperacute • Preformed Ab; immediate: “in the OR” • ABO incompatible or high titre donor specific HLA Class I Ab • Acute • T-cell mediated; days to weeks • Treatment and prevention via T-cell depletion: ATG or IL-2R blocker • Chronic (CAN) • Kidneys IF/TA • Immune and non-immune mechanisms • Difficult to predict, prevent, or belay

37. Alternative: ANTIBODY vs CELLULAR rejection

38. THE END • Thank you and Good Luck!