10.2: Lymphocytes

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: An image from a peripheral blood smear showing a small lymphocyte (A) and a large lymphocyte (B). 50x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R3JH3DH6Q

: An image from a normal peripheral blood smear showing two large lymphocytes. 100x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R30Z71C10

: An image from a peripheral blood smear showing a small lymphocyte. 50x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R3H12VP79

: An image from a peripheral blood smear with a neutrophil (left) and a small lymphocyte (right). 100x oil immersion. From MLS Collection, University of Alberta, https://doi.org/10.7939/R3930P92Z

Notes: Can be characterized as being small or large depending on the amount of cytoplasm. Small lymphocytes are more uniform in appearance whereas large lymphocytes have a variable appearance.¹

Nucleus-to-Cytoplasm Ratio: 5:1 to 2:1 ^1,2

Nucleoli: May be visible ^1,2

Nucleus:^1,2

Round, oval, or indented

Dark purple, dense chromatin (heterochromatin)

Cytoplasm:^1,2

Pale blue

Scant to moderate

Vacuoles may be present

Granules:^1,2

Large: Azurophilic granules may be present

Small: typically lack granules (agranular)

Normal % in Bone Marrow: 5-15% ²

Normal % in Peripheral Blood: 20-40% ²

Lymphocyte Lineage

Lymphocytes can be characterized into two cell types depending on the site of cell maturation:

1. B Cells

Lymphocytes that mature in the bone marrow. These cells are lymphocytes that are able to mature into plasma cells and take part in antibody production.¹

Specific surface markers:^1,3

CD10, CD19, CD20, D21, CD22, D24, CD38

2. T Cells

Lymphocytes that mature in the thymus and lymphoid tissues. When these cells become activated, they are able to take part in cell-mediated immunity.¹

Specific surface markers:^1,3

CD2, CD3, CD4, CD5, CD7, CD8, CD25

References:

1. Williams L, Finnegan K. Lymphocytes. In: Clinical laboratory hematology. 3rd ed. New Jersey: Pearson; 2015. p. 122-43.

2. Rodak BF, Carr JH. Lymphocyte maturation. In: Clinical hematology atlas. 5th ed. St. Louis, Missouri: Elsevier Inc.; 2017. p. 79-88.

3. Czader M. Flow cytometric analysis in hematologic disorders. In: Rodak’s hematology clinical applications and principles. 5th ed. St. Louis, Missouri: Saunders; 2015. p. 543-60.