Lymphocytes are the second most common circulating white blood cell (roughly 20-40%). Most circulating lymphocytes are resting until stimuli causes them to differentiate.
They are important in fighting viral infections.
Appearance
Resting lymphocytes are small with scant dark blue cytoplasm. The nucleus is about the size of a red blood cell with dark and clumpy chromatin.
Lookalikes
Nucleated red blood cells can be mistaken for lymphocytes, as they both have scant basophilic cytoplasm and are similar in size. However, earlier red cell precursors will have a distinct nucleus with a cartwheel pattern. More mature nucleated red cells typically have a more condensed nucleus and pinker cytoplasm.
