A child born with the inability to develop either cell- or antibody-mediated immunity is diagnosed with
Why does the risk of cancer increase in AIDS patients?
A)Suppressor T cell activity resets the normal immune response.
B)Immune surveillance is depressed.
C)Cell-mediated immunity is enhanced.
D)There is an increase in the circulating antibody levels.
E)The virus enters human leukocytes by receptor-mediated endocytosis.
Changes in the immune system that accompany aging include
A)T cells becoming less responsive to antigens.
B)more cytotoxic T cells responding to infections.
C)increased numbers of T helper cells.
D)higher levels of antibodies after initial exposure to antigens.
E)enlargement of the thymus and increased levels of circulating thymic hormones.
The increased incidence of cancer in the elderly reflects the fact that
A)immune surveillance increases.
B)tumor cells are eliminated effectively.
C)their diets do not meet nutritional standards.
D)everyone is prone to disease.
E)immune surveillance declines with age.