Definitions / Recently Added

Powerful chemical substances secreted by lymphocytes. These molecules help direct and regulate the immune responses.

FK Reading Ease
13.1

FK Grade Level
College
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  • An organ of the immune system where lymphocytes develop and congregate. These organs include the bone marrow, thymus, lymph nodes, spleen, and various other clusters of lymphoid tissue. Blood vessels and lymphatic vessels are also lymphoid organs.

    FK Reading Ease
    50.3

    FK Grade Level
    High School
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  • A small white blood cell produced in the lymphoid organs and essential to immune defenses. B cells, T cells, and NK T cells are lymphocytes.

    FK Reading Ease
    75.7

    FK Grade Level
    Elementary School
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  • A bodywide network of channels, similar to the blood vessels, which transports lymph to the immune organs and into the bloodstream.

    FK Reading Ease
    52.6

    FK Grade Level
    High School
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  • A small bean­shaped organ of the immune system, distributed widely throughout the body and linked by lymphatic vessels. Lymph nodes are garrisons of B and T cells, dendritic cells, macrophages, and other kinds of immune cells.

    FK Reading Ease
    52.3

    FK Grade Level
    High School
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  • A transparent, slightly yellow fluid that carries lymphocytes, bathes the body tissues, and drains into the lymphatic vessels.

    FK Reading Ease
    42.9

    FK Grade Level
    High School
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  • FK Reading Ease
    54.7

    FK Grade Level
    Middle School
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  • A protein produced by cells that stimulates antivirus immune responses or alters the physical properties of immune cells.

    FK Reading Ease
    28.8

    FK Grade Level
    College
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  • An immune system function that is inborn and provides an all-­purpose defense against invasion by microbes.

    FK Reading Ease
    40.3

    FK Grade Level
    High School
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  • Redness, warmth, and swelling produced in response to infection; the result of increased blood flow and an influx of immune cells and their secretions.

    FK Reading Ease
    60.7

    FK Grade Level
    Middle School
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