Lymphocytes
Lymphocytes, such as NK cells, are characterized by their large nuclei that actively absorb Wright stain and, therefore, appear dark colored under a microscope.
Source
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"OpenStax College, Innate Immune Response. October 17, 2013."
http://cnx.org/content/m44820/latest/Figure_42_01_05.jpg
OpenStax CNX
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