IMMUNOLOGY

Detailed explanation-1: -Memory immune responses After the first encounter with a pathogen, our immune systems generate a small number of cells that remain for a long time, are specific for that pathogen, and circulate in the blood, spleen and lymph nodes to keep watch for another encounter.

Detailed explanation-2: -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. One type of phagocyte is the neutrophil (NOO-truh-fil), which fights bacteria.

Detailed explanation-3: -To fight infections, the immune system must be able to identify pathogens. Pathogens have molecules called antigens on their surface. Antigens provide a unique signature for the pathogen that enables immune system cells to recognize different pathogens and distinguish pathogens from the body’s own cells and tissues.

Detailed explanation-4: -One of the most remarkable features of the immune system is its ability to “remember” past encounters with pathogens like viruses, bacteria, and parasites. This phenomenon, known as immunological memory, is controlled by two main immune cell types: memory T and B cells.

Detailed explanation-5: -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.