Video Transcript
What is a cytokine? (A) An enzyme that destroys
microbes in the blood and other body fluids. (B) A phagocyte that is active
during an inflammatory response. (C) A chemical messenger that
mediates communication between immune cells. (D) A globular protein that binds
specifically to antigens. Or (E) a structure in the lymph
node where lymphocytes mature.
The human immune system is
responsible for preventing and fighting off infection and illness. Immune responses can be broadly
divided into two components: cell-mediated immunity, which relies on the function of
cells such as T and B lymphocytes and macrophages, and humoral immunity, which
relies on the function of chemicals such as antibodies in the blood.
One of the major components of
humoral immunity is the production of cytokines, a group of signaling chemicals that
serve many different functions. They are made by and act upon a
wide variety of cells, including the cells responsible for cell-mediated
immunity. As a result, cytokines help to
balance cell-mediated and humoral immunity. They also regulate immune cell
maturation and help the many types of immune cells communicate with each other. There are several different types
of cytokines, including chemokines, interferons, interleukins, and lymphokines. Scientists continue to research
their many roles and complex interactions.
Let’s look more closely at the
cytokines known as interleukins. Humans have genes that code for at
least 50 types of interleukins, which are produced rapidly as a result of a stimulus
such as infection. The term “interleukin” means
between white blood cells, because scientists originally thought interleukins were
only produced by and acted upon leukocytes. However, in recent years, it’s been
discovered that many other cell types both secrete and have receptors for
interleukins. For example, skeletal muscle cells
secrete interleukin-6 after prolonged exercise.
Interleukins have an enormous
variety of functions, including stimulating the growth, differentiation, and
movement of T and B cells, responding to viral infections, and exerting both
inflammatory and anti-inflammatory effects in the body. Scientists continue to study these
ubiquitous and complex molecules, including their use as a cancer treatment.
Based on what we’ve learned about
interleukins and other cytokines, we can now conclude that the correct answer is
(C). A cytokine is a chemical messenger
that allows communication between immune cells.
