biology

Interleukin 6

Interleukin 6 is a biology topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Interleukin 6 rather than just read about it. In short: Interleukin 6 (IL-6) is an interleukin that acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine. In humans, it is encoded by the IL6 gene.

Key takeaways

Interleukin 6 belongs to biology; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Interleukin 6 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Interleukin 6 from memory before moving on to harder problems.

Reference excerpt

Interleukin 6 (IL-6) is an interleukin that acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine. In humans, it is encoded by the IL6 gene. In addition, osteoblasts secrete IL-6 to stimulate osteoclast formation. Smooth muscle cells in the tunica media of many blood vessels also produce IL-6 as a pro-inflammatory cytokine. IL-6's role as an anti-inflammatory myokine is mediated through its inhibitory effects on TNF and IL-1 and its activation of IL-1ra and IL-10. There is some early evidence that IL-6 can be used as an inflammatory marker for severe COVID-19 infection with poor prognosis, in the context of the wider coronavirus pandemic.

Function

Immune system IL-6 is secreted by macrophages in response to specific microbial molecules, referred to as pathogen-associated molecular patterns (PAMPs). These PAMPs bind to an important group of detection molecules of the innate immune system, called pattern recognition receptors (PRRs), including Toll-like receptors (TLRs). These are present on the cell surface and intracellular compartments and induce intracellular signaling cascades that give rise to inflammatory cytokine production. IL-6 is an important mediator of fever and of the acute phase response. IL-6 is responsible for stimulating acute phase protein synthesis, as well as the production of neutrophils in the bone marrow. It supports the growth of B cells and is antagonistic to regulatory T cells.

Metabolic It is capable of crossing the blood–brain barrier and initiating synthesis of PGE2 in the hypothalamus, thereby changing the body's temperature setpoint. In muscle and fatty tissue, IL-6 stimulates energy mobilization that leads to increased body temperature. At 4 °C, both the oxygen consumption and core temperature were lower in IL-6-/- compared with wild-type mice, suggesting a lower cold-induced thermogenesis in IL-6-/- mice. In the absence of inflammation 10–35% of circulating IL-6 may come from adipose tissue. IL-6 is produced by adipocytes and is thought to be a reason why obese individuals have higher endogenous levels of CRP. IL-6 may exert a tonic suppression of body fat in mature mice, given that IL-6 gene knockout causes mature onset obesity. Moreover, IL-6 can suppress body fat mass via effects at the level of the CNS. The antiobesity effect of IL-6 in rodents is exerted at the level of the brain, presumably the hypothalamus and the hindbrain. On the other hand, enhanced central IL-6 trans-signaling may improve energy and glucose homeostasis in obesity Trans-signaling implicates that a soluble form of IL-6R (sIL-6R) comprising the extracellular portion of the receptor can bind IL-6 with a similar affinity as the membrane bound IL-6R. The complex of IL-6 and sIL-6R can bind to gp130 on cells, which do not express the IL-6R, and which are unresponsive to IL-6. Studies in experimental animals indicate that IL-6 in the CNS partly mediates the suppression of food intake and body weight exerted by glucagon-like peptide-1 (GLP-1) receptor stimulation. Outside the CNS, it seems that IL-6 stimulates the production of GLP-1 in the endocrine pancreas and the gut. Amylin is another substance that can reduce body weight, and that may interact with IL-6. Amylin-induced IL-6 production in the ventromedial hypothalamus (VMH) is a possible mechanism by which amylin treatment could interact with VMH leptin signaling to increase its effect on weight loss. It is assumed that interleukin 6 in the liver activates the homologue of the human longevity gene mINDY expression via binding to its IL-6-receptor, which is associated with activation of the transcription factor STAT3 (which binds to the binding site in the mIndy promoter) and thereby rise of citrate uptake and hepatic lipogenesis.

Central nervous system Intranasally administered IL-6 has been shown to improve sleep-associated consolidation of emotional memories. There are indications of interactions between GLP-1 and IL-6 in several parts of the brain. One example is the parabrachial nuclei of the pons, where GLP-1 increases IL-6 levels and where IL-6 exerts a marked anti-obesity effect.

… excerpt ends here. Continue reading the full article.

Illustrations

Worked examples

Example 1 — a first encounter with Interleukin 6

Start with the simplest possible case. Write down what Interleukin 6 claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In biology, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Interleukin 6 before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Interleukin 6 ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Interleukin 6

In research: Interleukin 6 appears in biology research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Interleukin 6 in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Interleukin 6 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Genes on human chromosome 7, Interleukins, Neurotrophic factors, so understanding it makes those chapters shorter.
In everyday life: Look for Interleukin 6 outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Interleukin 6 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Interleukin 6 means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Interleukin 6 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Interleukin 6 in simple terms?

Interleukin 6 (IL-6) is an interleukin that acts as both a pro-inflammatory cytokine and an anti-inflammatory myokine. In humans, it is encoded by the IL6 gene.

Why does Interleukin 6 matter?

Because it connects several biology ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Interleukin 6?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Interleukin 6.