CYTOKINES

Cytokines are important because: Master regulators of the immune system Therapeutic reagents Master regulators of the immune system Therapeutic reagents

Cytokine Nomenclature Monokines - cytokines produced by moncytes Lymphokines - cytokines produced by activated T cells Interleukins - cytokines produced by leukocytes which act leukocytes Interferons - cytokines important in controlling viral infections and augmenting immune responses Colony-Stimulating Factors - cytokines important in the maturation of leukocytes Chemokines - cytokines important in directed migration of leukocytes during immune responses Growth Factors - cytokines involved in stem cell differentiation and other functions Monokines - cytokines produced by moncytes Lymphokines - cytokines produced by activated T cells Interleukins - cytokines produced by leukocytes which act leukocytes Interferons - cytokines important in controlling viral infections and augmenting immune responses Colony-Stimulating Factors - cytokines important in the maturation of leukocytes Chemokines - cytokines important in directed migration of leukocytes during immune responses Growth Factors - cytokines involved in stem cell differentiation and other functions

Cytokine Functions Are: PLEIOTROPIC REDUNDANT SYNERGISTIC ANTAGONISTIC PLEIOTROPIC REDUNDANT SYNERGISTIC ANTAGONISTIC

CYTOKINE PROPERTIES Low molecular weight proteins or glycoproteins Synthesized in active and inactive forms Secretion is brief and self-limiting Active at very low concentrations Signal cells by binding to specific receptors on target cells Low molecular weight proteins or glycoproteins Synthesized in active and inactive forms Secretion is brief and self-limiting Active at very low concentrations Signal cells by binding to specific receptors on target cells

Cytokine Receptors Each cytokine has a receptor Receptors are grouped into 5 families Cytokine receptors are often multi- chain complexes Signaling through receptors requires multiple events Each cytokine has a receptor Receptors are grouped into 5 families Cytokine receptors are often multi- chain complexes Signaling through receptors requires multiple events

IL-1 IL-2 IL-8 and chemokines IFN- , ,  TNF- , 

Cytokine Receptor Subfamilies Signaling receptor subunit Cognate receptor subunit

Generalized Cytokine Signaling Mechanism  -Chain Cognate receptor  -Chain Cognate receptor  -Chain Signaling receptor  -Chain Signaling receptor JAK P P P P P P P P P P P P Transcription P P P P STATs Nuclear membrane

Cytokine Effects on Target Cells are: AUTOCRINE - PARACRINE - ENDOCRINE - AUTOCRINE - PARACRINE - ENDOCRINE -

Hematopoietic Cytokines in the Immune System

Cytokines are critical for lymphocyte development

T Cell Maturation and Cytokines Dependent on IL-2 for activation, growth and proliferation after Ag binding Differentiation to helper T cell subsets (Th1 and Th2) depends on cytokines Th1 cells produce cytokines that aid cell- mediated immunity (IFN- , IL-2, others) Th2 cells produce cytokines that aid antibody production (IL-4, IL-5, others) Dependent on IL-2 for activation, growth and proliferation after Ag binding Differentiation to helper T cell subsets (Th1 and Th2) depends on cytokines Th1 cells produce cytokines that aid cell- mediated immunity (IFN- , IL-2, others) Th2 cells produce cytokines that aid antibody production (IL-4, IL-5, others)

Dependent on multiple cytokines for activation, growth and proliferation after Ag binding IL-6 is a major growth factor for B cells Multiple cytokines are involved in isotype switching (e.g., TGF-  for IgA, IL-4 for IgE) Dependent on multiple cytokines for activation, growth and proliferation after Ag binding IL-6 is a major growth factor for B cells Multiple cytokines are involved in isotype switching (e.g., TGF-  for IgA, IL-4 for IgE) B Cell Maturation and Cytokines

Cytokines in Host Defense Viral Infections Cytokines in Host Defense Viral Infections Viruses infect by binding to a “receptor” and are internalized Take-over host machinery, replicate DNA or RNA Viral genetic material is recognized as foreign by TLRs (TLR3 - dsRNA, TLR8 - ssRNA) Viral TLR binding leads to production of “Interferons” - anti-viral cytokines critical to clearing viral infections

Viral Responsive TLRs ssRNA

INTERFERONS Two Major Interferons:Types I and II Type I: produced by all cells (IFN-  /  ) Type II: produced by act. T cells (IFN-  ) Functions: innate immunity - viral clearance adaptive immunity - lymphocyte activation/maturation Functions: innate immunity - viral clearance adaptive immunity - lymphocyte activation/maturation

Interferon anti-viral mechanisms Induce the expression of MHC molecules Shut down infected host cells - Allows Ag presentation to cytotoxic T cells - Loss of MHC expression allows targeting by NK cells - Allows Ag presentation to cytotoxic T cells - Loss of MHC expression allows targeting by NK cells - production of 2-5 (A) synthase -> activates RNAse L -> degrades mRNA - PKR inactivates eIF-2 (a translation factor) -> blocks protein synthesis - production of 2-5 (A) synthase -> activates RNAse L -> degrades mRNA - PKR inactivates eIF-2 (a translation factor) -> blocks protein synthesis

Cytokines in Host Defense Bacterial Infections Cytokines in Host Defense Bacterial Infections Bacteria infect by a number of routes - ingested, inhaled, through cuts Take over a niche and replicate rapidly Bacterial PAMPS are recognized as foreign by TLRs (TLR4 - LPS, TLR5 - flagellin) Bacterial PAMP binding to TLRs leads to production of pro-inflammatory cytokines and the acute phase response, critical to clearing bacterial infections

Bacterial PAMP Responsive TLRs

ACUTE PHASE RESPONSE A well orchestrated sequence of events to mobilize a metabolic response of the organism to: Eliminate invading pathogens Prevent on-going tissue damage Activate repair processes A well orchestrated sequence of events to mobilize a metabolic response of the organism to: Eliminate invading pathogens Prevent on-going tissue damage Activate repair processes Mediated by “pro-inflammatory” cytokines including TNF- , IL-1, IL-6, IL-8 and IFN- 

Tumor Necrosis Factor-  (TNF-  ) Interleukin 6 (IL-6) Interleukin 1 (IL-1) Tumor Necrosis Factor-  (TNF-  ) Interleukin 6 (IL-6) Interleukin 1 (IL-1) Production induced by LPS and other PAMPS, made by MØ, fibroblasts, others Activates myeloid cells, epithelium, endothelium Induce production of multiple cytokines Initiates acute phase response (fever) Induces adhesion molecule expression Toxic at high levels (septicemia) Production induced by LPS and other PAMPS, made by MØ, fibroblasts, others Activates myeloid cells, epithelium, endothelium Induce production of multiple cytokines Initiates acute phase response (fever) Induces adhesion molecule expression Toxic at high levels (septicemia)

Acute Phase Proteins Host Defense Proteins Proteinase Inhibitors Anti-oxidants Host Defense Proteins Proteinase Inhibitors Anti-oxidants CRP, complement, fibrinogen C1 inhibitor,  1-proteinase inhibitor Haptoglobin, ceruloplasmin

Chemokines Multiple families of small molecular weight cytokines (at least 60 at present time) Classified based on different cysteine motifs Involved in multiple immune functions including inflammation, cell recruitment, lymphocyte trafficking, lymphoid organ development and wound healing Expressed in primary and secondary lymphoid organs Multiple families of small molecular weight cytokines (at least 60 at present time) Classified based on different cysteine motifs Involved in multiple immune functions including inflammation, cell recruitment, lymphocyte trafficking, lymphoid organ development and wound healing Expressed in primary and secondary lymphoid organs

Clinical Applications of Cytokines Some of your patients will be receiving cytokine therapy for non-dental/optometry conditions Cytokine-specific therapies are in use for some dental/optometry conditions Some of your patients will be receiving cytokine therapy for non-dental/optometry conditions Cytokine-specific therapies are in use for some dental/optometry conditions

Cytokine Therapy Interferon-  therapy for chronic myeloid leukemia - disease remission Soluble TNF-  receptor (Infliximab) - therapy for rheumatoid arthritis Interferon-  therapy for multiple sclerosis - effective in about 30% of patients Procrit (erythropoietin) to boost RBC levels in patients undergoing chemotherapy

Cytokine Therapy for the Eye Anti-TNF-  antibody in refractory posterior uveitis - restored visual acuity Nerve growth factor heals corneal ulcers refractory to conventional therapy - no side effects Interferon-  treatment of Bechet’s disease reduces retinal inflammation, improves visual acuity

Cytokine Therapy for the Oral Cavity Thalidomide (anti-TNF-  ) therapy for orofacial granulomatosis - clinical resolution Soluble TNF-  receptor therapy prevents root resorption in a rat model system Interferon-  therapy combined with surgery clinically resolves aggressive oral giant cell tumors