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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-3 and CSF)
Cytokine actions
1) Pleiotropy
Acts on more than one cell type (IL-4)
2) Redundancy
More than one cytokine have the same action (IL-2, IL-7,IL-15)
3) Synergy
Introduction to cytokines Categories of CKs Biological function of CKs Cytokine receptor Clinical application of cytokines
Introduction to cytokines
Interleukin, IL
Cytokines produced by leukocytes and act on leukocytes
IL-1~35 IL-2, IL-7, IL-9, IL-15 constitute common chain family IL-4, IL-5, IL-6, IL-13 (Th2 type) IL-8 (belongs to chemokine family) IL-10 (Tr type) IL-11 (stimulator of platelets) IL-12 (DC, macrophages, directs Th1)
Tumor necrosis factor, TNF
TNF was originally identified (and was so named) as a substance that can cause the necrosis of tumors in vivo.
The target cell needs to have a receptor on its surface
Therefore, regulation can occur at either step.
General properties of CKs
Small proteins (MW: approx. 8-30 KD) Extremely potent, acting at 10-9~10-15M The production is transient and tightly regulated Autocrine, paracrine or endocrine Cytokine actions: Pleiotropy, Redundancy, Synergy
4) Antagonism
Two or more cytokines work against each other (IL-4 and IFN-)
The cytokine network:
Many cytokines have multiple functions and apparent redundancy of actions forming a complex communication network.
Cytokine (CK) Cytokines are small soluble proteins that mediate immune and inflammatory reactions and are responsible for communications between leukocytes and other cells.
Categories of CKs
CKs are classified into 6 functional categories
Interleukin (IL) Interferon (IFN) Tumor necrosis factor (TNF) Colony stimulating factor (CSF) Chemokine Growth factor (GF)
Interferon, IFN
IFNs are mediators of the innate immune response and Th1/CTL responses.
Groups Type I IFN: IFN- and IFN- The major source is leukocytes (PDC), fibroblasts Help prevent the spread of virus to uninfected cells. Type II IFN: IFN- IFN- is produced by activated T cells and NK cells. Its main function is immune regulation.
Cytokines work by binding to a target cell. Therefore, for a cytokine to have an effect, two things have to occur:
The cytokine needs to be present there
and Antagonism
Manner of action
1) Autocrine: IL-2 Th
Th
2) Paracrine : IL-12 DC
Biblioteka Baidu
Th
3) Endocrine: IL-1, TNF-
Under certain circumstances (e.g. septic shock), large amounts of CKs (such as TNF-) are produced, they may be active distant from their site of secretion.
