The Innate Immune Response to Bacterial and Fungal Infections

What Really Happens During the Lag Period Before the Acquired Immune Response? Innate immunity Acquired immunity

Distinctions Between Innate and Adaptive Immunity Innate immune system Adaptive immune system Receptors Germline-encoded Somatically engineered Distribution Non-clonal Clonal Kinetics Rapid Slow (requires clonal expansion) Specificity Recognizes non-self Recognizes “altered self” through “Pattern recognition” Primary structure (TCR) Higher order structure (Immunoglobulin; BCR) Effector Cells All Primarily lymphocytes, M 

The Innate Immune Response is Conserved Throughout Evolution and is Triggered by Pattern Recognition

Lipopolysaccharide is Composed of Lipid and Polysaccharide From: Beutler and Rietschel, Nature Reviews Immunology 3 ; (2003)

The Complement System is Critical for Innate Immunity and is Triggered by Multiple Ligands

Soluble “Defense Collagens” Participate in Innate Immunity

Pseudomonas aeruginosa CRD (6 X 3) Collagen domain Domain Structure of Surfactant Protein A (SP-A), a Lung Soluble Defense Collagen (Collectin) Alveolar macrophage

Phagocytosis is Mediated by Receptors of the Innate Immune System and the Acquired Immune System

Examples of “Pattern Recognition Receptors” that Participate in Innate Immunity Receptor Expression Target Ligand Integrins CR3 (CD11b/CD18;  M  2 ) PMN, Mo, M  Yeast  -glucan CR3 (CD11b/CD18;  M  2 ) PMN, Mo, M  Yeast  -glucan C3bi, fibrinogen, LPS, ICAM C3bi, fibrinogen, LPS, ICAM  1 Integrins LeukYersinia Invasin  3 Integrin (?  v  3 ) M  Osteopontin Scavenger Receptors SR-AI/SR-AII M  Gram-positive bacteria Leipoteichoic acid SR-AI/SR-AII M  Gram-positive bacteria Leipoteichoic acid Gram-negative bacteria ? Gram-negative bacteria ? MARCO M  E. coli, S. aureus ? MARCO M  E. coli, S. aureus ? Collectin Receptors C1qR p PMN, Mo, M  C1q, SPA, MBL C1qR p PMN, Mo, M  C1q, SPA, MBL gp-340 M  SP-D, SP-A gp-340 M  SP-D, SP-A SPR210 Mo, M  SPA Lectins SPR210 Mo, M  SPA Lectins Dectin-1 M , DC  Yeast   -1,3-/  -1,6 glucans Dectin-1 M , DC  Yeast   -1,3-/  -1,6 glucans CR3 (CD11b/CD18;  M  2 ) PMN, Mo, M  Yeast  -glucan CR3 (CD11b/CD18;  M  2 ) PMN, Mo, M  Yeast  -glucan CD14 Mo, M , soluble Gram-negative bacteria LPS Gram-positive bacteria Peptidoglycan Gram-positive bacteria Peptidoglycan Toll-like Receptors TLR2 M , imDC Gram-positive bacteria Peptidoglycan, Leipoteichoic acid TLR2 M , imDC Gram-positive bacteria Peptidoglycan, Leipoteichoic acid Mycobacteria Lipoarabinomannan Mycobacteria Lipoarabinomannan Spirochetes Lipoproteins, Lipopeptides Spirochetes Lipoproteins, Lipopeptides Mycoplasmas Lipopeptides Mycoplasmas Lipopeptides TLR4 M  Gram-negative bacteria LPS TLR4 M  Gram-negative bacteria LPS

SREC LOX-1 CD 68 dSR-C ISR-B1 CD 36MARCO SR-A II N NN N NN N N N N N N CC C C C SR-A I N N N C C C C C C C C C C * * SR-CSR-B C C C N N N SR-A SR-A III -Complement control protein (CCP) -Somatomedin B -C-type Lectin -Epidermal growth factor (EGF) -Partial Epidermal growth factor (EGF) -Potential N-linked glycosylation -Potential O-linked glycosylation KEY TO DOMAINS SR-DSR-ESR-F The Scavenger Receptor Superfamily LTA LPS Gram-positive bacteria Gram-negative bacteria Bacterial DNA E. coli S.aureus E. coli S.aureus E. coli S.aureus

Receptors Important in The Systemic Response to Infection

History of Endotoxin Research From: Beutler and Rietschel, Nature Reviews Immunology 3 ; (2003)

Core LPS Signaling Machinery c From: Beutler and Rietschel, Nature Reviews Immunology 3 ; (2003)

An Innate Immunity “Time Line” Use of adjuvant to stimulate the immune response Modified from: Beutler and Rietschel, Nature Reviews Immunology 3 ; (2003) Discovery of the NF-  B signaling pathway by Toll in Drosophila by Hoffman and colleagues Molecular basis of adjuvant discovered by Medzhitov and Janeway “Infectious-non-self” model of immunity described by Janeway

TRAF6dTRAF Vertebrates Drosophila TLR-4 Toll ECSIT dECSIT DD TIR domain MyD88 Tube IRAK Pelle NF-  B MEKK1 IKK-  p65 Cactus Dif/Relish Ird6 extracellular space cytosol TAK IKK-  IKK-  MD2 CD14 Adaptor proteins Kinases IKK complex p50 I-  B Receptor Complex TLR Signaling Components TIR = Toll/IL-1 receptor DD = Death domain IKK = I-  B kinase

NOD Proteins: Intracellular Peptidoglycan Sensors NF-  B p65 p50 I-  B RICK Nod Protein CARD Ligand Recognition NOD-1 NOD-2

Recruitment of TLR2 to Yeast Phagosomes TLR2 Phase Contrast TLR2 From: Underhill et al., Nature 401:811, 1999

From: Luster, Curr. Opin. Immunol. 14:129, 2002

The Dendritic Cell and Development of The Primary Immune Response

From: Mellman & Steinman, Cell 106:255, 2001 Dendritic Cell Maturation

From: Luster, Curr. Opin. Immunol. 14:129, 2002 The Innate Immune Response Orchestrates DC Trafficking to Secondary Lymphoid Organs

Functional Differences Between Immature and Mature DCs Expression of CCR7 Migration towards T-cell zone of lymph node

The (Primary) Acquired Immune Response is Initiated by Innate Immune Recognition

From: Luster, Curr. Opin. Immunol. 14:129, 2002 Chemokines Direct Trafficking of Immune Cells

The Dual Role of Defensins in Bacterial Immunity

 -pleated sheets are represented by green arrows; arginine and lysine residues are shown in blue From: Perez-Canadillas et al., J. Bio.l Chem :28372 Chemokine CCL20  -defensin BD2

Inflamed defenders. A model of defensin activity in an infected epithelium. Epithelial cells synthesize antimicrobial defensins (red) both constitutively and in response to infectious and inflammatory stimuli. Other defensins are introduced by the influx of phagocytic cells that use them to kill ingested microbes. Released defensins attract dendritic cells and memory T cells, setting the stage for the adaptive phase of the immune response. From Ganz, Science 286:420, The Role of Defensins in Orchestrating the Immune Response

The Innate Immune Response to Viruses

The Early Antiviral Response: Cytokines of the Innate Immune System

From: Siegal et al., Science 284:1746, 1999 A Subset of Peripheral Blood Dendritic Cells Produce IFN-  Tracing and isolation of IPCs/pDC2s from human peripheral blood. CD3+ T cells, CD19+ B cells, CD16+ and CD56+ NK cells, and CD14+ monocytes were depleted from blood mononuclear cells by immunomagnetic beads (Dynabeads M-450; Dynal, Oslo, Norway). The cells were stained with anti-CD4- Tricolor (Immunotech, Marseille, France), anti-CD11c- PE (Becton Dickinson, San Jose, California), and a mixture of fluorescein isothiocyanate-labeled antibodies to CD3, CD15, CD16, CD20, CD57 (Becton Dickinson), CD14 (Coulter, Miami, Florida), and CD34 (Immunotech). Within the lineage-negative population (A), CD4+CD11c IPCs and CD11c+ immature DCs were isolated (B). IPCs are plasmacytoid by Giemsa staining (C) and contain rough endoplasmic reticulum and Golgi apparatus under transmission electron microscopy (D). The CD11c+ blood immature DCs display dendrites (E and F)

The Antiviral Response: a Cascade of Transcriptional Events Multiphasic induction of murine type I IFN genes can be divided into three phases. (a) The immediate early phase. Virus infection stimulates a phosphorylation cascade, leading to the activation of at least three families of transcription factors, including NF-  B, AP-1 and IRF3. Activation of the IFN-  promoter requires all three transcription factors. (b) IRF7 induction phase. Secretion of early IFN produces an autocrine response through stimulation of the JAK-STAT pathway. Among the pathway’s target genes is IRF7, itself. (c) Delayed early (amplification) phase. Many members of the IFN-  gene family possess promoter binding sites for activated IRF7 and become transcriptionally active. Some targets of IRFs GeneFunction p21 Cell cycle arrest IL-15 NK cell maturation FasL Cell death IL-12Th1 immune response

CD56 bright natural killer (NK) cells are the major producers of NK-derived cytokines following activation of monocytes. (a) During the innate immune response, when macrophages (M  ) encounter pathogens they produce a variety of cytokines which can then activate the production of IFN-  by NK cells. In turn, NK-cell-derived IFN-  is requisite for the elimination of intracellular pathogens and the further activation of production of cyotkines by M . In this setting, the CD56 bright NK-cell subset produces significantly more IFN-  protein compared with the CD56 dim NK-cell subset, as shown in (b). Resting CD56 bright and CD56 dim NK cells were co-cultured with autologous, lipopolysaccharide (LPS)-activated macrophages (M  + LPS) in vitro. Note that NK cells cultured with unstimulated M  did not produce IFN- . Data represent the mean ± SD of 7 experiments. (From: Cooper et al., Trends Immunol. 22:633, 2001) NK Cells are an Important Early Source of IFN- 