Part
Four - Molecular Biology: The Genome in Action 331
18.
Immunology: Gene Expression and Natural Defense
Systems 400
18.1
What Are the Major Defense Systems
of Animals? 401
Blood and lymph tissues play important
roles in defense systems 402
White blood cells play many defensive
roles 402
Immune system proteins bind pathogens
or signal other cells 403
18.2 What Are
the Characteristics of the Nonspecific
Defenses? 404
Barriers and local agents defend the
body against invaders 404
Other nonspecific defenses include
specialized proteins and cellular
processes 405
Inflammation is a coordinated response
to infection or injury 406
A cell signaling pathway stimulates
the body’s defenses 407
18.3 How
Does Specific Immunity Develop? 407
The specific immune system has four
key traits 407
Two types of specific immune responses
interact 408
Genetic changes and clonal selection
generate the specific immune response
408
Immunity and immunological memory
result from clonal selection 409
Vaccines are an application of immunological
memory 409
Animals distinguish self from nonself
and tolerate their own antigens 410
18.4 What
Is the Humoral Immune Response? 411
Some B cells develop into plasma cells
411
Different antibodies share a common
structure 411
There are five classes of immunolo
globulins 412
Monoclonal antibodies have many uses
413
18.5
What Is the Cellular Immune Response?
414
T cell receptors are found on two
types of T cells 414
The MHC encodes proteins that present
antigens to the immune system 415
Helper T cells and MHC II proteins
contribute to the humoral immune response
417
Cytotoxic T cells and MHC I proteins
contribute to the cellular immune
response 417
MHC proteins underlie the tolerance
of self 417
18.6
How Do Animals Make So Many Different
Antibodies? 418
Antibody diversity results from DNA
rearrangement and other mutations
418
The constant region is involved in
class switching 419
18.7
What Happens When the Immune System
Malfunctions? 420
Allergic reactions result from hypersensitivity
420
Autoimmune diseases are caused by
reactions against self antigens 421
AIDS is an immune deficiency disorder
421
