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USMLE® Step 1 questions

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USMLE® Step 1 style questions USMLE

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A study is done on the inflammatory response in the body. The study found that many immune cells and cytokines play a role in coordinating the immune response. One of the primary cells involved was macrophages. Which of the following is true about the roles of macrophages and the cytokines it produces?  

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recombinant cytokines for p. NaN

Chronic granulomatous disease (CGD) p. NaN

recombinant cytokines for p. NaN

Cytokines p. 99, 106

corticosteroids and p. 118

Graves disease and p. 348

rejection reactions p. 117

type IV hypersensitivity p. 111

Helper T cells

cytokine secretion p. 106

Immune responses p. 102-115

cytokines p. 106

Macrophages p. 415

cytokine secretion p. 106

Metastatic melanoma

recombinant cytokines for p. NaN

Multiple sclerosis p. 541

recombinant cytokines for p. NaN

Recombinant cytokines p. NaN

Renal cell carcinomas p. 623

recombinant cytokines p. NaN

T cells p. 411

cytokine production p. 99, 106

Thrombocytopenia p. 415

recombinant cytokines p. NaN


Cytokines are tiny proteins that are secreted by both immune and non-immune cells to communicate with one another. Cytokines bind to receptors and trigger a response in the receiving cell. Oftentimes, cytokines promote activation, proliferation, and differentiation of immune cells, but they can do other things like help increase the body temperature - causing a fever.

Now, cytokines signal to other cells mainly through autocrine and paracrine signaling; but to a lesser extent, endocrine signaling can also be employed. Now, autocrine means the cell producing the cytokine is also the cell responding to the cytokine. An example is Interleukin-2, or IL-2 which is secreted by CD4+ T helper cells. IL-2 promotes the proliferation of T lymphocytes - including the CD4+ T helper cell that produced it. Paracrine means that the cytokine is produced by one cell and that it affects cells in the near vicinity. Once again, an example is IL-2 because it helps nearby CD8+ cytotoxic T cells proliferate. That’s important because the CD8+ cytotoxic T cells aren’t good at making their own IL-2. Finally, there’s endocrine, which is when the cytokine affects a cell that’s far away, perhaps in a different organ. An example would be the inflammatory triad of Interleukin 1-beta or IL-1beta, Interleukin-6 or IL-6, and Tumor Necrosis Factor-alpha, or TNF-alpha. These cytokines are produced by macrophages and dendritic cells. During acute inflammation, these cytokines travel to the liver and the brain. In response, the liver produces acute phase reactants like C-reactive protein and Mannose Binding Lectin, and the brain increases the body’s temperature, triggering a fever. At the same time, IL-1beta and TNF-alpha also help to recruit other immune cells to the site of injury, enhancing the inflammatory response.


Cytokines are cell signaling proteins that play an essential role in the regulation of immune responses, including inflammation and cell growth. There are many different cytokines, and they can be classified into five main classes. They include Interleukins, Tumor Necrosis Factors, Interferons, Transforming Growth Factors, and colony-stimulating factors.


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