biology

Interleukin 7

Interleukin 7 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 7 rather than just read about it. In short: Interleukin 7 (IL-7) is a protein that in humans is encoded by the IL7 gene. IL-7 is a hematopoietic growth factor secreted by stromal cells in the bone marrow and thymus.

Key takeaways

Interleukin 7 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 7 to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Interleukin 7 from memory before moving on to harder problems.

Reference excerpt

Interleukin 7 (IL-7) is a protein that in humans is encoded by the IL7 gene. IL-7 is a hematopoietic growth factor secreted by stromal cells in the bone marrow and thymus. It is also produced by keratinocytes, follicular dendritic cells, hepatocytes, neurons, and epithelial cells, but is not produced by normal lymphocytes. A study also demonstrated how the autocrine production of the IL-7 cytokine mediated by T-cell acute lymphoblastic leukemia (T-ALL) can be involved in the oncogenic development of T-ALL and offer novel insights into T-ALL spreading.

Structure The three-dimensional structure of IL-7 in complex with the ectodomain of IL-7 receptor has been determined using X-ray diffraction.

Function

Lymphocyte maturation IL-7 stimulates the differentiation of multipotent (pluripotent) hematopoietic stem cells into lymphoid progenitor cells (as opposed to myeloid progenitor cells where differentiation is stimulated by IL-3). It also stimulates proliferation of all cells in the lymphoid lineage (B cells, T cells and NK cells). It is important for proliferation during certain stages of B-cell maturation, T and NK cell survival, development and homeostasis. IL-7 is a cytokine important for B and T cell development. This cytokine and the hepatocyte growth factor (HGF) form a heterodimer that functions as a pre-pro-B cell growth-stimulating factor. This cytokine is found to be a cofactor for V(D)J rearrangement of the T cell receptor beta (TCRß) during early T cell development. This cytokine can be produced locally by intestinal epithelial and epithelial goblet cells, and may serve as a regulatory factor for intestinal mucosal lymphocytes. Knockout studies in mice suggested that this cytokine plays an essential role in lymphoid cell survival.

IL-7 signaling

IL-7 binds to the IL-7 receptor, a heterodimer consisting of Interleukin-7 receptor alpha and common gamma chain receptor. Binding results in a cascade of signals important for T-cell development within the thymus and survival within the periphery. Knockout mice which genetically lack IL-7 receptor exhibit thymic atrophy, arrest of T-cell development at the double positive stage, and severe lymphopenia. Administration of IL-7 to mice results in an increase in recent thymic emigrants, increases in B and T cells, and increased recovery of T cells after cyclophosphamide administration or after bone marrow transplantation.

Disease

Cancer IL-7 promotes hematological malignancies (acute lymphoblastic leukemia, T cell lymphoma).

Viral Infections Elevated levels of IL-7 have also been detected in the plasma of HIV-infected patients.

Clinical application IL-7 as an immunotherapy agent has been examined in many pre-clinical animal studies and more recently in human clinical trials for various malignancies and during HIV infection.

Cancer Recombinant IL-7 has been safely administered to patients in several phase I and II clinical trials. A human study of IL-7 in patients with cancer demonstrated that administration of this cytokine can transiently disrupt the homeostasis of both CD8+ and CD4+ T cells with a commensurate decrease in the percentage of CD4+CD25+Foxp3+ T regulatory cells. No objective cancer regression was observed, however a dose limiting toxicity (DLT) was not reached in this study due to the development of neutralizing antibodies against the recombinant cytokine.

HIV infection Associated with antiretroviral therapy, IL-7 administration decreased local and systemic inflammations in patients that had incomplete T-cell reconstitution. These results suggest that IL-7 therapy can possibly improve the quality of life of those patients.

Transplantation IL-7 could also be beneficial in improving immune recovery after allogenic stem cell transplant.

References

Illustrations

Worked examples

Example 1 — a first encounter with Interleukin 7

Start with the simplest possible case. Write down what Interleukin 7 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 7 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 7 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 7

In research: Interleukin 7 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 7 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 7 is common in secondary-school and first-year university syllabi. It links to neighbouring topics Cancer treatments, Genes on human chromosome 8, Immunomodulating drugs, so understanding it makes those chapters shorter.
In everyday life: Look for Interleukin 7 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 7 in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Interleukin 7 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 7 out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Interleukin 7 in simple terms?

Interleukin 7 (IL-7) is a protein that in humans is encoded by the IL7 gene. IL-7 is a hematopoietic growth factor secreted by stromal cells in the bone marrow and thymus.

Why does Interleukin 7 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 7?

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 7.