Lecture 22 Cytokines as Therapeutics Flashcards
What are cytokines?
These are proteins, polypeptides, or glycopeptides.
These are signalling molecules that mediate interactions between cells of the immune system.
These mediate immune, inflammatory responses as well as hematopoiesis.
These act at the nano to pico molar range.
How are cytokines classed?
Cell of origin:
lymphokine, monotone
Function: chemokine: chemotaxis GM-CSF (colony stimulating factors) Interleukins Interferons Tumor necrosis factors.
Structural or sequence homology
What is a main issue with how cytokines are classified?
Various cell types can secrete the same cytokine and one cytokine can have various functions depending on which cell secreted it.
What are the general effects in a Th1 response?
Pro-immunity
Pro-inflammatory
Il-2, TNFa, INFy
What are the general effects of the Th2 response?
Repair and recovery of tissues damaged by infection and inflammation.
Allergic response
Anti-inflammatory
Il-4, Il-10, Il-13
How does Th1/Th2 balance/imbalance affect an immune response?
An imbalance other than present during infection is associated with autoimmune diseases, hypersensitivity, and cancer.
Normal Th1 prevalence is pro-inflamatory whereas Th2 prevalence is anti-inflammatory.
What is Il-2?
AKA T cell growth factor.
Binds IL-2 receptor on lymphocytes
Pro-inflammatory cytokine induces Th1 response.
Secreted by Cd4+ cells
Results in expansion and proliferation of lymphoid cells esp. B and NK cells.
Induces secretion of other cytokines like TNF as well as antibodies.
Role in antiviral/bacterial immune response.
Role in selection of regulatory T cells.
Role in suppression of self-anti-self recognition to maintain tolerance.
Also has role in promoting apoptosis, Th2, and other immunosuppressive actions.
What are some therapeutic uses of Il-2?
Metastatic renal cell carcinoma
Acute myeloid leukaemia
Why are the therapeutic uses of IL-2 limited?
It has toxicity when used outside of its natural role.
It can induce:
Autoimmune disorders
Capillary leak syndrome
Cardiac, CNS, Renal and liver toxicity.
What are interferons and what are the main types?
These are secreted in response to and interfere with viral replication.
Type 1: INF-a/B
Type 2: INF-y
What is the immunostimulatory role of type 1 interferons?
These induce resistance to viral replication in cells.
These promote the Th1 response
These induce secretion of IL-15 (ligand) by macrophages which act on receptors on NK cells promotes their differentiation in order to kill virus infected cells.
Il-15 also promotes differentiation of memory T cells.
NK cells are induced by type 1 interferon actions to secrete type 2 interferon INF-y among other things.
What are the roles of Type 2 Interferons?
INF-y is secreted by NK cells.
This is immunostimulatory, activating antigen presenting cells and increases proliferation of other cells in the Th1 response.
This is a potent inflammatory cytokine.
This targets macrophages in tissues resulting in further macrophage activation.
Macrophages become more efficient at phagocytosis and destruction of pathogens and are induced to secrete inflammatory cytokines themselves.
There are also some immunosupressive roles:
What are the immunosuppressive functions of type 1 INFs?
These act to increase IL-10, which inhibits secretion of inflammatory cytokines.
These act to decrease IL-12 leading to a decrease in stimulation of inflammation.
Il 12 is secreted by macrophages to cause the activation and recruitment of NK cells into effector NK cells which then act on macrophages and other cells in the infected tissue to produce a heightened state of inflammation.
What are some therapeutic uses for INF?
infections diseases, cancers, autoimmune diseases
Hep B, C, hair cell leukaemia
What are some potential issues with use of INF?
May precipitate autoimmune diseases like:
auto-immune thyroiditis
lupus
rheumatoid arthritis.
Treatment with cytokines mimics the natural progress of some diseases where these cytokines are upregulated.
What is INF-a2a used for and how does it help?
Hep C (acute and chronic)
Hep B (chronic)
Leukemias (chronic myeloid and hair cell leukaemia.
Lymphoma (non-hodgkin’s)
Mechanism: this decreases cell proliferation and differentiation and decreases replication of virus-infected cells.
What are some side effects of INF a2a use?
Immunosuppression (easier infection)
Myelosuppression
autoimmune diseases
Headache, fatigue, fever
How is INF-a2a currently formulated?
PEGylated INF-a2a (Pegasys) for subcutaneous injection
What is INF-a2b used for and how does it act?
Chronic Hep B and C
Hair cell leukaemia
Non-Hodgkin’s lymphoma
Decreases cell proliferation and differentiation
Decreases virally-infected cell replication.
What are some major adverse effects of INF-a2b?
Allergic and hypersensitivity reactions.
Chest pain
Fatigue, fever, headache.
Myelosuppression.