AP BIOLOGY

THE HUMAN IMMUNE SYSTEM

IMMUNE RESPONSE

Question [CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
Example of 3rd line of defense.
A
T cells and B cells reacting to pathogens
B
Phagocytes engulfing pathogens
C
Hydrochloric acid killing pathogens
D
Mucus and cilia catching pathogens
Explanation: 

Detailed explanation-1: -The third line of defence is called the immune response and is SPECIFIC. It involves the production of two types of lymphocytes (B and T cells) which are specific to the invading particle. They work together to attack the pathogen.

Detailed explanation-2: -The third line of defense is specific resistance. This system relies on antigens, which are specific substances found in foreign microbes. Most antigens are proteins that serve as the stimulus to produce an immune response.

Detailed explanation-3: -B cells create antibodies. These antibodies bind to pathogens or to foreign substances, such as toxins, to neutralize them. For example, an antibody can bind to a virus, which prevents it from entering a normal cell and causing infection. B cells can also recruit other cells to help destroy an infected cell.

Detailed explanation-4: -Lymphocyte There are two main types of lymphocytes: B cells and T cells. The B cells produce antibodies that are used to attack invading bacteria, viruses, and toxins. The T cells destroy the body’s own cells that have themselves been taken over by viruses or become cancerous.

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