Interleukin Main Function Key Clinical Associations
IL‑1 Major pro‑inflammatory cytokine; ↑ adhesion molecules; ↑ nitric oxide, prostacyclin → vasodilation Septic shock hypotension (vasodilation) ; fever (acts on hypothalamus)
IL‑2 T‑cell growth factor; stimulates T & B lymphocyte proliferation Used in immunotherapy (renal cell carcinoma); not responsible for sepsis hypotension
IL‑3 Supports haematopoietic progenitor cell growth Myeloid lineage support; activates neutrophils/macrophages
IL‑4 Drives Th2 differentiation; class switching to IgE & IgG Allergy, atopy, asthma pathways; regulates antibody production
IL‑5 Growth & activation of eosinophils; class switching to IgA Eosinophilic asthma; helminth infections; biologics (mepolizumab)
IL‑6 Acute phase reactants (CRP, fibrinogen); fever Sepsis; inflammatory disorders; cytokine storm
IL‑7 T‑cell survival & development Lymphocyte maturation (especially T cells)
IL‑8 Potent neutrophil chemoattractant (“clean up on aisle 8”) Pyogenic infections; neutrophil recruitment
IL‑10 Anti‑inflammatory; inhibits Th1 cytokines Autoimmune regulation; reduces IL‑1, IL‑6, TNF
IL‑12 Drives Th1 differentiation; ↑ IFN‑γ Intracellular infections; NK cell activation

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“1 HOT, 2 T‑cells, 3 STEMS, 4 IgE, 5 Eosino, 6 SICK, 7 SURVIVE, 8 ATTRACT, 10 CALM, 12 TH1.”

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IL-1

Interleukin 1 (IL-1) is a key mediator of the immune response. It is secreted mainly by macrophages and monocytes and acts as a costimulator of T cell and B cell proliferation.

Other effects include increasing the expression of adhesion molecules on the endothelium. By stimulating the release by the endothelium of vasoactive factors such as PAF, nitric oxide and prostacyclin it also causes vasodilation and increases vascular permeability. It is therefore one of the mediators of shock in sepsis. Along with IL-6 and TNF, it acts on the hypothalamus causing pyrexia.

IL-1 inhibitors are increasingly used in medicine. Examples include: