Cytokines Dr habil Khidai Lszl Assoc Professor Dept

Cytokines Dr. habil. Kőhidai László Assoc. Professor Dept. Genetics, Cell- and Immunobiology Semelweis University Chemotaxis - Elective Course 2019 – EM-ED

Cytokines - Definition • ”Cytokine” (Cohen 1974): • Molecules capable for chemical communication between cells; • Most of them are growth factors or differentiation inducers; • Regulators of embryogenesis, haematopoesis, tissue ‘repair’, inflammatory and immune functions. E. g. normal growth and development, wound healing. • Lymphokines, monokines, chemokines

Characterization of cytokines Summary • Proteines / glycoproteines • Narrow spectrum • Work in solved form • Network • Low M. W. • Multifunctionality • Inducibility • Synergy • Effects elicited on low cc. • Progression factor • Specific receptors • Competency factor

Grouping - Functions • Natural immunity and inflammation (IFN, TNF, IL-1, IL-6, chemokines) • Regulating of lymphocyte activity, differenctiation (IL-2, IL-5, IL-6) • Maturation of immune cells (IL-3, GM-CSF)

Characteristics • Low M. W. 15 -25 k. Da • Products of leukocytes – BUT other cells can also produce them • Production induced by Ø Ø infectious substances and toxins (e. g. LPS) tissue damage (thrombocyte aggregation) immune iductions (stages of hypersensitivity) other cytokines e. g. IL-1 (pro-inflammatory cytokines) • Constitutive – e. g. IL-16, IL-18, EPO, M-CSF

Characteristics • Majority of cytokines are released by the cells before action BUT there are Ø membrane bound forms (TNF), Ø pooled in i. c. vesicles i. c. (mast cells vagy thrombocyte) Ø stored in extra-cellular matrixban (TGF-beta) – rapid release and action • Narrow action radius Ø autocrine – cytokine produced by the cell acts on the producer cell Ø paracrine – cytokine acts on the neighbour cells of the producer cell Ø endocrine – cytokine acts on cells far from the producer cell IL-1 from site of injury to thalamus – regulation of temperature IL-6 from site of injury to liver – acut phase reaction Erythropoetin from kidney to bone marrow – RBC differentiation

Macrophage Cytotoxicity ^ Monokine prod. ^ Adhesion mol. ^ Autocrine IL-1 T cell Activation ^ IL-2 R ^ Lymphokines ^ Paracrine Endocrine Prostaglandins Pain threshold Brain Fever

Characteristics • Effects on low concentrations : 10 -12 – 10 -9 M ! 10 IL-1 molecules are enough to induce IL-2 synthesis in T cells ! ! 50 IFN gamma molecules are enough to induce anti-viral effects !

Receptors • Specific receptors: high affinity, inducibility, specific intracellular signal-transduction and second messenger pathways.

• Cytokine networks: cytokines are never produced alone, their synthesis is controlled by the balance of positive and negative signals.

inflammation Defense against infections Immune- Autoimmunity, rejection suppression

Characteristics • Synery : combined effetc of two or more cytokines is higher than the simple summary of the individual effects • Antagonism : cytokines can block each other e. g. IL-4 and IFN-g. • Multifunctionality: (pluripotent , pleiotrope) several cytokines possess more, different effects on the diverse target cells • Progressive factor: cytokines induce cell proliferation (IL-2, IL-3, IL-5) • Competency factor: inducing of differentiation (IL-1, IL-4, IL-6)

Nomenclature Factors (names) describe the function - Historical Ø colony stimulating factor CSF Ø tumor necrosis factor TNF Ø transforming growth factor TGF Classification based on characteristic gene sequence – result of joint agreement Ø IL-1 – IL-24 Names describing the structure and function Ø chemotactic factors - ‘chemokins’.

Regulation • DNA-level Ø genes turned on continously e. g. M-CSF, G-CSF, SCF, IL-6, Epo génjei Ø other genes of cytokines are turned off Ø co-ordinated expression e. g. IL-3, IL-4, IL-5, GM-CSF genes on 5. Chrs q • Post-transcription level • Post-secretion level Ø short half life time in serum e. g. TNF = 15 min Ø soluble cytokine receptors, e. g. s. TNF-R • Target cell Ø up- and down-regulation of receptors Ø induction or amplification of inflammation by i. e. proinflammatory cytokines

Examples IL-1 – produced by all cells possessing nucleus, nucleus its spectrum is wide, it has several target cells. In vivo effects: hypotensio, fever, loss of weight, neutropoenia and acut phase reaction. The chief function is elicited as a factor released from dendritic cells Promotes proliferation of T lymphocytes IL-3 – haematopoetic growth factor, inducer of colony formation in erythroid, megakaryocyte, neutrophil, eosinophil, basophil, mast cell and monocyte cell lines.

Examples IL-6 – multifunctional cytokine, cytokine produced by lymphoid and non-lymphoid cells. Regulator of B-cell funkcions, kcions haematopoesis and the acut phasis reakction IL-8 - cytokine released in inflammation, inflammation several cells can produce it, It works as chemoattractant in neutrophils. Can also influence activity of basophils and some subpopulations of lymphocytes. Effective angiogen factor.

Examples IL-12 – important in responses against intracellular pathogens. Inducer of IFN gamma synthesis in T-cells and in NK cells. Increases the NK and ADCC activity. Inducer of proliferation and differentiation in Th 1 CD 4 cells.

Clinical significance • auto-immune diseases • infections • immune-defficiencies • malignant tumors