Chapter 14

Question 1

Immunologic tolerance is what?

Answer 1

unresponsiveness to an
antigen induced by the exposure of specific lymphocytes to that antigen. Tolerance to self antigens
is a fundamental property of the normal immune
system, and the failure of self-tolerance leads to
autoimmune diseases

Question 2

Antigens may be administered in ways that induce tolerance rather than
immunity, and this may be exploited how?

Answer 2

for the prevention and treatment of transplant rejection and

autoimmune and allergic diseases.

Question 3

Central tolerance is induced where?

Answer 3

in the generative lymphoid organs (thymus and bone marrow) when
immature lymphocytes encounter self antigens
present in these organs

Question 4

Peripheral tolerance occurs when?

Answer 4

mature lymphocytes recognize self antigens

in peripheral tissues under particular conditions

Question 5

In T lymphocytes, central tolerance (negative

selection) occurs when

Answer 5

immature thymocytes with
high-affinity receptors for self antigens recognize
these antigens in the thymus. Some immature
T cells that encounter self antigens in the thymus
die and others develop into FoxP3+
regulatory
T lymphocytes, which function to control responses
to self antigens in peripheral tissues

Question 6

In CD4+
T cells, anergy is
induced by what?

Answer 6

antigen recognition without adequate
costimulation or by engagement of inhibitory
receptors like CTLA-4 and PD-1

Question 7

Regulatory T cells

inhibit immune responses in part by producing what?

Answer 7

immunosuppressive cytokines. T cells that encounter self antigens without other stimuli or that are
repeatedly stimulated die by apoptosis.

Question 8

In B lymphocytes, central tolerance is induced

when immature B cells recognize what?

Answer 8

multivalent self
antigens in the bone marrow. The usual result is
the acquisition of a new specificity, called receptor
editing, or apoptotic death of the immature B cells

Question 9

Mature B cells that recognize self antigens in the
periphery in the absence of T cell help may be
rendered what?

Answer 9

anergic and ultimately die by apoptosis
or become functionally unresponsive because of
the activation of inhibitory receptors

Question 10

Autoimmunity results from what?

Answer 10

a failure of selftolerance. Autoimmune reactions may be triggered by environmental stimuli, such as infections,
in genetically susceptible individuals

Question 11

Most autoimmune diseases are what?

Answer 11

polygenic, and
numerous susceptibility genes contribute to disease
development. The greatest contribution is from
MHC genes; other genes are believed to influence
the selection or regulation of self-reactive
lymphocytes.

Question 12

Infections may predispose to autoimmunity by

several mechanisms, including what?

Answer 12

enhanced expression of costimulators in tissues and cross-reactions
between microbial antigens and self antigens.
Some infections may protect individuals from
autoimmunity, by unknown mechanisms.