IFN gamma is secreted by all except
[A] NK cells
[B] TH1 cells
[C] TH2 cells
[D] Macrophases
Answer = [C] TH2 Cells (Ref: Kelley’s Textbook of Rheumatology)
TH1 cells >> Secrete >> IFN-Gamma, which activates macrophages by the classical pathway.
TH2 cells secrete IL-4, IL-5, and IL-13, which recruit and activate eosinophils and leads to activation of macrophases by >> Alternative pathway of macrophage activation. TH2 cells do not produce IFN- Gamma.
Major cell sources of IFN Gamma = Macrophase/TH1 Cells/B cells/NK Cells/yST cells/DCs
Key Functions OF IFN Gamma are:-
Macrophage activation
Dendritic Cell Antigen Presenting function * Endothelial adhesion molecule expression MHC class Il expression 7S
T cell growth |
Bone resorption
Opposes Th2 responses
Hot Shots >> Cytokines
e |L-1 (IL-1 > TNF) is the most important cytokine responsible for the systemic effects of inflammation.
e IL-6 is the most important cytokine causing liver synthesis and release of Acute phase reactants.
e The endogenous pyrogens or pyrogenic cytokines include IL-1, IL-6, TNF, Ciliary neurotopic factor (CNTF), IFN-a
e IFN-Gamma have above defined role whereas IFN-a and IFN-8 inhibit viral growth.
e Cytokines that mediate innate immunity - IL-1, TNF, IFN, IL-6. IL-12
Cytokines regulating lymphocyte growth, activation and differentiation
e |L-2 >> T-cell growth factor
e |L-4 >> Promotes differentiation of T cells to TH2 pathway.
e |L-12 >>Promotes differentiation of T cells to TH1 pathway.
e [L-15 >> Stimulates the growth and activity of NK cells.
e |L-10 and TGF-b are antinflammatory and so down regulate immune responses.
Cytokines that activate inflammatory cells Eg IL-5 is most potent cytokine activator of eosinophils.
Cytokines that affect chemotaxis > Chemokines
Cytokines that stimulate hematopoiesis e.g. GM-CSF, G-CSF, stem cell factor
The Anti inflammatory cytokines are IL-10, TGF-B, IL-4, IL-13
IL-4 >> Involved in class swithch to IgE ie the secretion of IgE from the B cells.
Isotype switching is induced by a combination of CD40 ligand-mediated signals and cytokines (e.g., IFN-y for IgG, IL-4 for IgE, and transforming growth factor in mucosal tissues for IgA), which are modulated by CD4 helper T cells.