HAEMOPOIETIC CYTOKINES AND SIGNALLING PATHWAYSDenise Pegnall

AIM

Understanding of the regulation of haemopoiesis

Haemopoietic Stem Cell Transcription factors Cytokines / Growth factors involved in

Haemopoiesis Haemopoiesis of different lineages Cytokine mode of action Cytokine Receptors Signalling Pathways

HAEMOPOIESIS

Haemopoiesis starts with stem cell division One cell replaces the stem cell The other cell is committed to differentiation

Embryonic yolk sac Mesenchyme of the yolk sac

Endothelial cells & Haemopoietic Stem Cells Early committed progenitor cells express low

levels of transcription factors that may commit them to the discrete cell lineages

PU.1 commits to myeloid lineage GATA-1 essential for erythroid and

megakaryocytes differentiation

Postgraduate H

aematology 5th E

d. 2005HAEMOPOIETIC TRANSCRIPTION FACTORS

REGULATION Extrinsic,intrinsic or both? Extrinsic

Cell-Cell interaction Cytokines

Small protein released by cells Interactions between cells, behaviour of cells Interleukins, lymphokines, cell signal molecules, interferons

Stem Cell Factor / receptor c-kit Flt3 ligand / receptor Flt3 Intrinsic

SCL, Stem cell leukaemia haemopoietic transcription factor GATA-2 Both required for haemopoiesis in the yolk sac

HAEMOPOIETIC ORGANISATION

Haemopoietic growth factors, (cytokines) Colony stimulating factors (CSF’s) Interleukins (IL’s)

SCF, IL-3,IL-6 : HSC CFU-L & CFU-GEMM (Stem Cells)

Thrombopoiesis Formed from CFU-Meg by endomitotic replication Megakaryocytes polyploid, 64n DNA content 2000-7000 platelets in each Megakaryocyte

Erythropoiesis mediated by Epo Decreased RBC leads to hypoxia increased Epo

synthesis

HAEMOPOIETIC ORGANIZATION

Lymphopoiesis: Lymphoid cell differentiates to Mature antigen committed lymphocytes in primary

lymphoid organs T lymphs differentiate in thymus gland B lymphs differentiate in foetal liver & adult bone marrow

Antigen dependent proliferation in secondary lymphoid organs B &T lymphs mature in spleen, lymph nodes, mucosa

associated lymphoid tissue

Granulopoiesis / Monopoiesis IL-3 & GM-CSF :CFU-GEMM BFU-E, CFU-Meg, CFU-GMEo, CFU-Baso

CFU-E, CFU-GM, CFUEo: CFU-G & CFU-M

HIERARCHICAL ORGANIZATION OF HAEMOPOIESIS

Adapted from Postgraduate Haematology 5th Ed. 2005

IL-3 &GM-CSF

IL-3EP0IL-4GM-CSF

SCFIL-3IL-6

IL-1,IL-3,IL-6

IL-3EPOGM-CSF

IL-3GM-CSFTPO

IL-3IL-5GM-CSF

CFU- Baso

Basophils

IL-3

M-CSFG-CSF

Postgraduate H

aematology 5th E

d. 2005

HAEMOPOIETIC CYTOKINES & THEIR TARGET CELLS

CYTOKINES & GROWTH FACTORS

Soluble regulators of blood cell production Produced by several cell types in different

sites in the body Glycoproteins

anti-parallel α helices joined by loops & β-sheets

Some exist also in membrane bound forms Lack sequence responsible for release from the

cell Haemopoietic progenitors require multiple

cytokines for optimal growth & development

CYTOKINES

Six major types of cytokine chemokines, colony-stimulating factors,

interferons, interleukins, transforming growth factors, and tumour necrosis factors (TNF)

Modes of action Autocrine, on cells that produce them Paracrine, on cells in the immediate vacinity Endocrine, on cells at a distance

Act in synergy or antagonistically Have pleiotropic actions

CYTOKINE RESPONSES AND SIGNAL TRANSDUCTION

Haemopoietic cell responses include Survival, proliferation, differentiation Stimulation of mature cell function

Modulate haemopoietic responses by accessing target cell receptors

Bind to receptors on cell surface Activates signal transduction pathways Transmits a signal to the nucleus Stimulates the transcription of regulatory

genes

SIGNALLING PATHWAYS

Haemopoietic cell function regulated by cytokines through activation of signal transduction pathways

Relevant to cell proliferation & differentiation Janus Kinase(Jak)/ Signal transducers and

activators of transcription (STATS) Mitogen-activated protein (MAP) Kinase Phosphatidylinisitol (PI)3-Kinase

Postgraduate H

aematology 5th E

d. 2005

JAK /STAT PATHWAY

Postgraduate H

aematology 5th E

d. 2005

JAK /STAT PATHWAY

Postgraduate H

aematology 5th E

d. 2005

GENERALIZED DIAGRAM OF THE SIGNAL TRANSDUCTION PATHWAYS ACTIVATED BY CYTOKINES AND THEIR RECEPTORS IN HAEMOPOIETIC CELLS

CYTOKINES RECEPTORS

Haemopoietic receptor cytokine superfamily Share a common Trp-Ser-X-Trp-Ser motif (X= any amino acid)

Two main types Single chain

Intrinsic tyrosine kinase domains G-CSF, Epo

Heterodimers (2 or more subunits) GM-CSF IL-3

Postgraduate H

aematology 5th E

d 2005

CYTOKINE RECEPTOR SUPERFAMILY

BASIC IMMUNOPHENOTYPES OF HAEMOPOIETIC STEM CELLS

POSITIVE NEGATIVE

CD34 CD33

Thy-1 CD38

AC133 Lineage Markers

c-Kit HLA-DR

Postgraduate haem

atology 5th Ed. 2005

E2F

Retinoblastoma