IMMUNOLOGY

Detailed explanation-1: -White blood cells, also called leukocytes (LOO-kuh-sytes), play an important role in the immune system. Some types of white blood cells, called phagocytes (FAH-guh-sytes), chew up invading organisms. Others, called lymphocytes (LIM-fuh-sytes), help the body remember the invaders and destroy them.

Detailed explanation-2: -phagocytes (say: FAH-guh-sytes), which chew up invading germs. lymphocytes (say: LIM-fuh-sytes), which allow the body to remember and recognize previous invaders.

Detailed explanation-3: -Natural killer (NK) cells are also lymphocytes. NK cells recognize and destroy cells that contain a virus.

Detailed explanation-4: -Both T lymphocytes (T cells) and B lymphocytes (B cells) can become memory cells.

Detailed explanation-5: -T lymphocytes are cells that are programmed to recognize, respond to and remember antigens.

Detailed explanation-6: -Some white blood cells-B cells (B lymphocytes)-can recognize invaders directly. But others-T cells (T lymphocytes)-need help from cells called antigen-presenting cells: Antigen-presenting cells ingest an invader and break it into fragments.

Detailed explanation-7: -The immune system keeps a record of every microbe it has ever defeated, in types of white blood cells (B-lymphocytes and T-lymphocytes) known as memory cells. This means it can recognise and destroy the microbe quickly if it enters the body again, before it can multiply and make you feel sick.