AP BIOLOGY

Detailed explanation-1: -The immune system recognizes invaders by their antigens, which are proteins on the surface of the invading cells (see Figure 1). Every cell or substance has its own specific antigens, and a person’s cells carry “self-antigens” that are unique to that individual.

Detailed explanation-2: -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 (also called immunoglobulins). These proteins lock onto specific antigens.

Detailed explanation-3: -The innate immune responses are the first line of defense against invading pathogens. They are also required to initiate specific adaptive immune responses. Innate immune responses rely on the body’s ability to recognize conserved features of pathogens that are not present in the uninfected host.

Detailed explanation-4: -Killer T cells protect the body from certain bacteria and viruses that have the ability to survive and even reproduce within the body’s own cells. In addition to fighting germs, killer T cells also recognize and respond to foreign tissues in the body, such as a transplanted kidney.