What is immunity? List four barriers that protect the body from the entry of foreign agents. or The outline structure of a drug is given below a)Which group of drugs does this represent? b) What are the modes of consumption of these drugs? c. Name the organ of the body that is affected by the consumption of these drugs.
Answers
Explanation:
The immune system is the body's defense against infections. The immune (ih-MYOON) system attacks germs and helps keep us healthy.
When the body senses foreign substances (called antigens), the immune system works to recognize the antigens and get rid of them.
B lymphocytes are triggered to make antibodies. These specialized proteins lock onto specific antigens. The antibodies stay in a person's body. That way, if the immune system encounters that antigen again, the antibodies are ready to do their job. That's why someone who gets sick with a disease, like chickenpox, usually won't get sick from it again.
This is also how immunizations (vaccines) prevent some diseases. An immunization introduces the body to an antigen in a way that doesn't make someone sick. But it does let the body make antibodies that will protect the person from future attack by the germ.
Although antibodies can recognize an antigen and lock onto it, they can't destroy it without help. That's the job of the T cells. They destroy antigens tagged by antibodies or cells that are infected or somehow changed. (Some T cells are actually called "killer cells.") T cells also help signal other cells (like phagocytes) to do their jobs.
Antibodies also can:
neutralize toxins (poisonous or damaging substances) produced by different organisms
activate a group of proteins called complement that are part of the immune system. Complement helps kill bacteria, viruses, or infected cells.
These specialized cells and parts of the immune system offer the body protection against disease. This protection is called immunity.