Chapter 15

Question 1

The interaction of the immune system with infectious organisms is a dynamic interplay of host
mechanisms aimed at what?

Answer 1

eliminating infections and
microbial strategies designed to permit survival in
the face of powerful defenses

Question 2

Different types of

infectious agents stimulate distinct types of what?

Answer 2

of
immune responses and have evolved unique
mechanisms for evading immunity. In some infections, the immune response is the cause of tissue
injury and disease.

Question 3

Innate immunity against extracellular bacteria is

mediated by what?

Answer 3

phagocytes and the complement

system (the alternative and lectin pathways).

Question 4

The principal adaptive immune response against

extracellular bacteria consists of what?

Answer 4

specific antibodies
that opsonize the bacteria for phagocytosis and
activate the complement system. Toxins produced
by such bacteria are neutralized by specific antibodies

Question 5

Innate immunity against intracellular bacteria is

mediated mainly by macrophages. However, intracellular bacteria are capable of what?

Answer 5

surviving and replicating within host cells, including phagocytes,
because they have developed mechanisms for
resisting degradation within phagocytes.

Question 6

Adaptive immunity against intracellular bacteria is

principally cell mediated and consists of what?

Answer 6

activation
of macrophages by CD4+
 T cells (as in DTH) as well
as killing of infected cells by CD8+
 CTLs. The characteristic pathologic response to infection by intracellular bacteria is granulomatous inflammation.

Question 7

Protective responses to fungi consist of innate

immunity, mediated by what?

Answer 7

neutrophils and macrophages, and adaptive cell-mediated and humoral
immunity. Fungi are usually readily eliminated by
phagocytes and a competent immune system,
because of which disseminated fungal infections
are seen mostly in immunodeficient persons.

Question 8

Innate immunity against viruses is mediated by what?

Answer 8

type I interferons and NK cells. Neutralizing antibodies protect against virus entry into cells early
in the course of infection and later if the viruses are released from killed infected cells

Question 9

The major

defense mechanism against established infection is what?

Answer 9

is
CTL-mediated killing of infected cells. CTLs may
contribute to tissue injury even when the infectious virus is not harmful by itself

Question 10

Viruses evade

immune responses by?

Answer 10

antigenic variation, inhibition of antigen presentation, and production of
immunosuppressive molecules

Question 11

Parasites such as protozoa and helminths give rise

to what?

Answer 11

chronic and persistent infections because innate
immunity against them is weak and parasites have
evolved multiple mechanisms for evading and
resisting specific immunity.

Question 12

The structural and
antigenic diversity of pathogenic parasites is
reflected in what?

Answer 12

the heterogeneity of the adaptive

immune responses that they elicit.

Question 13

Protozoa

that live within host cells are destroyed by what?

Answer 13

cellmediated immunity, whereas helminths are eliminated by IgE antibody and eosinophil-mediated
killing as well as by other leukocytes.

Question 14

Parasites evade the immune system by?

Answer 14

varying their antigens during residence in vertebrate hosts, by
acquiring resistance to immune effector mechanisms, and by masking and shedding their surface
antigens.

Question 15

Vaccination is a powerful strategy for preventing
infections. The most effective vaccines are those
that stimulate the production of what?

Answer 15

high-affinity antibodies and memory cells. Many approaches for
vaccinating are in clinical use and being tried for
various infections.