Properties of cytokines Proteins Low molecular weight 口 Bind to receptor on either cell which produced it or another cell Receptor binding triggers a signal Signal results in altered pattern of gene expression
Properties of cytokines ◼ Proteins ◼ Low molecular weight ◼ Bind to receptor on either cell which produced it or another cell ◼ Receptor binding triggers a signal ◼ Signal results in altered pattern of gene expression
Cytokines can act in three different manners Autocrine Cytokine binds to receptor on cell that secreted it Paracrine Cytokine binds to receptors on near by cells Endocrine Cytokine binds cells in distant parts of the body
Cytokines can act in three different manners ◼ Autocrine ◼ Cytokine binds to receptor on cell that secreted it ◼ Paracrine ◼ Cytokine binds to receptors on near by cells ◼ Endocrine ◼ Cytokine binds cells in distant parts of the body
Cytokine Actions Pleiotropy Act on more than one cell type (INFa/B) Redundancy More than one cytokine can do the same thing (IFNo/βand IFNy) 口 Synergy Two or more cytokines cooperate to produce an effect that is different or greater than the combined effect of the two cytokines when functioning separately (IL-12 and IL-8) Antagonism Two or more cytokines work against each other (IL-4 and IL-12)
Cytokine Actions ◼ Pleiotropy ◼ Act on more than one cell type (INFa/b) ◼ Redundancy ◼ More than one cytokine can do the same thing (IFNa/b and IFNg) ◼ Synergy ◼ Two or more cytokines cooperate to produce an effect that is different or greater than the combined effect of the two cytokines when functioning separately (IL-12 and IL-8) ◼ Antagonism ◼ Two or more cytokines work against each other (IL-4 and IL-12)
How can non-specific cytokines act specifically? Only cells expressing receptors for specific cytokines can be activated by them Many cytokines have very short half-lives Only cells in close proximity will be activated High concentrations of cytokines are needed for activation Only cells in close proximity will be activated May require cell-to cell contact
How can non-specific cytokines act specifically? ◼ Only cells expressing receptors for specific cytokines can be activated by them ◼ Many cytokines have very short half-lives ◼ Only cells in close proximity will be activated ◼ High concentrations of cytokines are needed for activation ◼ Only cells in close proximity will be activated ◼ May require cell-to cell contact
Five cytokine receptor families Immunoglobulin superfamily receptors Class I cytokine receptor family (hematopoietin receptors) Binds most of the cytokines in the immune and hematopoietin systems Class II cytokine receptor family TNF receptor family Chemokine receptor family
Five cytokine receptor families ◼ Immunoglobulin superfamily receptors ◼ Class I cytokine receptor family (hematopoietin receptors) ◼ Binds most of the cytokines in the immune and hematopoietin systems ◼ Class II cytokine receptor family ◼ TNF receptor family ◼ Chemokine receptor family