White Blood Cells — the Body's Defenders

What you do

• Add up the five percentage ranges and check they come to roughly 100.
• Explain why a white cell is better named a white cell than a white blood cell — it spends about 90 per cent of its life outside the blood.

Challenges to clear

• Fill the non-granular column first — there are fewer of them, so be sure which.
• Now sort every card into its family.
• Fill the Granular box — the white cells whose cytoplasm is full of grains.

The task

Stained under a microscope, the five kinds of white cell fall into two families. Sort each card into its family.

What this lesson covers

• Granular — Grainy cytoplasm, nucleus constricted into lobes: Neutrophils, 55 to 70 per cent (The commonest white cell by far, with a 3 to 4 lobed nucleus that stains with neutral dyes. About 125 billion are made each day and each lives only a few hours.); Eosinophils, 1 to 3 per cent (A two-lobed nucleus and large granules that stain dark red with eosin, an acid dye. Their count rises in allergies.); Basophils, 0.5 to 1 per cent (The rarest white cell. Its granules take up basic dyes such as methylene blue, and its nucleus is large and indistinctly lobed.); Releases histamine, so vessels widen and the area inflames (This is the basophil at work. Widened vessels bring more blood and more defenders to the injured spot — that is the redness, heat and swelling of inflammation.); The chief phagocyte, first to engulf invading bacteria (Neutrophils lead the phagocytosis. Pus is mostly the dead white cells left behind after such a fight, mixed with destroyed tissue cells.); Cytoplasm packed with grains; nucleus pinched into lobes (These two features are the definition of the granular family, and all three of its members are made only in the bone marrow.)
• Non-granular — Clear cytoplasm, one single large nucleus: Lymphocytes, 20 to 35 per cent (The smallest of the white cells, with a single large nucleus and no granules at all. Made in bone marrow and in the lymph glands such as the spleen and tonsils.); Monocytes, 3 to 8 per cent (The largest of the white cells, with a big kidney-shaped nucleus. At the site of infection it transforms into a macrophage and ingests germs.); Produces antibodies that neutralise toxins (Lymphocytes make antibodies, which act as antitoxins and circulate freely in the plasma. Antibodies persisting after recovery are what make you immune, and are the principle behind vaccination.); Cytoplasm plain and clear; one single large nucleus (This is the definition of the non-granular family — only two members, the smallest white cell and the largest one.); Turns into a macrophage once it reaches infected tissue (Only the monocyte does this. Like all white cells it reaches the tissue by diapedesis, oozing out through the capillary wall.)

Hint

Say Never Eat Basil for the granular three — Neutrophil, Eosinophil, Basophil — and everything else is non-granular. Trap: lymphocytes have no granules and never release histamine, and monocytes are the largest white cells while lymphocytes are the smallest. Total count is only 4000 to 8000 per cubic millimetre; above about 50,000 signals infection.