Lymphocytes

(azure II and eosin)

• In a blood smear, their diameter may vary:
  • 6-7 μm – small lymphocytes (about 90% of the total lymphocyte number)
  • 8-10 μm – medium lymphocytes
  • > 10 μm – large lymphocytes (seldom found in the blood)
• The nuclei are hyperchromatic, rounded or bean-shaped
• The cytoplasm is basophilic
• Lymphocytes are classified into B cells, T cells, and NK cells (natural killers); the last ones are large lymphocytes with granules (contain azurophilic granules). Blood smears are not representative for their identification, and immune phenotype testing is required for this

Small lymphocytes q.v. #1, #2, #3, #4. Medium lymphocytes #1, #2. Large lymphocyte

Lymphocytes recirculate between the blood and tissues as immunocompetent cells. When upregulated by antigens in lymphoid organs, T and B cells enlarge, divide and form cell clones.

Depending on their type, the lifespan of lymphocytes ranges from several weeks to several years. Their relative cell blood count is 20-35% of the total WBC number, including about 70-80% of Т cells, 10-20% of B cells, and 5-10% of NK cells.

For more details see Electron microscopy image of lymphocytes

Monocytes

(azure II and eosin)

• Their diameter reaches 20 μm in blood smears
• The nucleus is bean-shaped or horseshoe-shaped with slightly condensed chromatin
• The cytoplasm is mildly basophilic containing small azurophilic granules

Monocytes q.v. #1, #2, #3

Monocytes circulate in the blood stream for a period between 8 hours and 3-4 days, then migrating to tissues to become macrophages. After that they provide non-specific and specific resistance of the body to alien factors. The lifespan of macrophages is different depending on the type of resident tissue; it lasts from 30 days to several years. Monocytes make up 3-8% of the total white blood cell count in the blood.

For more details see Electron microscopy image of a monocyte