Basic Immunology in Medical Practice

น.พ. สกานต์ บุนนาค งานโรคไต กลุ่มงานอายุรศาสตร์ รพ.ราชวิถี Basic immunology • Innate immunity • Ready to be used • Less specificity • Comprise of • External barriers: skin, mucus, washing fluid etc. • Molecule: complement, acute-phase protein and cytokine • inflammatory mediator secreting cells: basophil, mast cell, eosinophil and natural killer cell • Phagocytic cells: neutrophil, monocyte, and macrophage Basis immunology • Adaptive immunity • Active after expose to specific Ag. • High specificity • Comprise of • Humoral immune response (HIR) : B lymphocyte, Memory B lymphocyte, plasma cell and antibody • Cell mediated immune response (CMIR) : T lymphocyte • Effector T lymphocyte • CD4+ T cell  Helper T cell (Th1, Th2, Th17 etc.) • CD8+ T cell  Cytotoxic T cell • Regulatory T lymphocyte • Memory T lymphocyte Innate immunity Cellular component of innate immunity

• Activated by pathogen-associated molecular patterns (PAMPs) via pattern reconition receptors (PRRs).

• PAMPs • Shared by a larged group of infectious agens • Unlikely to mutate • Clearly distinguishable from self pattern (commonly not present on mammalian cell surface • Gram-negative LPS, gram-positive lipoteichoic acid, yeast cell wall mannan etc.

Phagocytic cells

• Neutrophils, monocyte and macrophage

• Killing machanisms • Reactive oxygen radicals • Oxygen-independent machanism: α – defencin, cathepsin G, lysozyme, lactoferin etc.

Mast cells Mast cells Natural killer (NK) cells Activating NK-R

FAS-L

perforin

FAS Granzyme-B

Caspase cascade target cell

Apotosis Natural killer (NK) cells Activating NK-R

Inhibitory NK-R FAS-L

perforin

self Ag FAS Granzyme-B MHC class I

Caspase cascade target cell

Apotosis Eoshinophils • Responsible for large parasites that can not be physically be phagocytosed.

• Use extracellular killing mechanism.

• Granules contain • reactive oxygen intermediates • Cationic protein (which damage the parasite membrane) Mannose pathway Properdin C3 Ag Or Microbial polysaccharide + MASP-1 C3bBb MBP (C3 convertase) (C3 convertase) Alternative pathway

MASP-2 C3bB Factor D C4b2a (C3 convertase) Ag-Ab complex C3b Factor B + C1qrs C4b2

C4 C4b C2 Classical pathway

Factor I

Factor H

iC3b (inactive) C5b-9 membrane attack complex Complement Functions fragments C3b • Phagocytic cells opsonization • Mast cells activation and secretion

C3a • Neutrophils activation • Eosinophils chemoattractant

C5a • Neutrophils activation • Neutrophils chemoattractant • increase vascular permiability

C5b-9 complex • Membrane attack complex Acute phase reactants • Response to alarm mediators of infection or tissue injury.

• Bind to a number of microorganisms

• Fixes complement (by classical pathway)

• Opsonizes

• C-reactive protein (CRP)

• Mannose binding protein (MBP)

• Serum amyloid P (SAP) : Amyloid precursor Cytokines

• Interleukins (IL) • Colony stimulating factors • Tumor necrotic factors • TNF-α • TNF-ß • Interferon (IFN) • Type 1 (IFN-α, IFN-ß) • Type 2 (IFN-Ɣ) • Others: TGF-ß etc. Adaptive immunity Major Histocompatibility Complex (MHC) molecule

• Major molecule for self vs. non-self determining process

• Very high antigenicity

• In human = human leukocyte Ag (HLA) Class I On the surface of all nucleated cells

Present intracellular Ag

Ag loading of MHC class-I Class II Antigen-presenting cells (APCs) monocyte, macrophage, Kuffer cell, dendritic cells, alveolar type2 cells, renal mesangial cells, and B lymphocyte

Present extracellular Ag

Ag loading of MHC class-II

Roitt’s Essential Immunology 11th Edition Specificity of T cells

Ag presenting cell Effecter T cells

Ag

Memory effecter Naïve T cell Activated T cell T cells

Regulatory T cell (suppressor T cell) CD4 Th1 CD TH2 _ _ 4 _ IL-2 IL-4 IFN- IL-5 TNF-ß IL-10 IL-13 + +

CMIR HIR T cell activation signal transduction

P. F. Halloran. N Engl J Med 2004; 351: 2715 3. Adhesion 1.Rolling and arrest 2.Activation

slex Integrin leukocyte

ICAM Selectin or VCAM

endothelium Cytotoxic T cells

T cell receptor

FAS-L

perforin Non-self Ag

FAS MHC class-I Granzyme-B

Caspase cascade target cell

Apotosis Ag Immature Ag B cell Activated

CD4+ T cell Mature B cell CD40L CD40

CD20 Clonal switching and hypermutation Memory B cell

Mature B cell

Mature Plasma B cell cell Mature B cell

antibody

Role of Ab

Target cell

NK cell or phagocytic cell Summary of CMIR Tolerance Central tolerance by thymic selection

Positive selection

Negative selection (central clonal deletion) Peripheral tolerance

N Engl J Med 2001; 344(9): 655-664 FOXP3: a specific marker of Tregs

• Ex-vivo activation of human CD4+ CD25- human T cells generates CD4+ CD25+ T cells expressing FOXP3 and suppressive function 1.

• FOXP3 gene transfer can convert human CD4+ T cell into Tregs 2.

• In humans, both CD4+ and CD8+ T cells can express FOXP3, but preferentially expressed in CD4+ CD25 high cells 1, 3.

1. Walker MR et al. J Clin Invest 2003: 112(9);1437. 2. Allan SE et al. J Clin Invest 2005: 115(11); 3276. 3. Veronese F et al. Am J Transplant 2007: 7(4); 914. How to identify Treg

Protein level

Tissue immunostaining

Flowcytometry

Gene level

PT-PCR

Gel electrophoresis