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Innate and
Adaptive
Immunity
13
Nancy A. Moriber
The
human body is constantly exposed to potentially
deleterious microorganisms and foreign substances. Therefore,
it has evolved a complete system composed of complemen-
tary and interrelated mechanisms to defend against invasion
by bacteria, viruses, and other foreign substances. Through
recognition of molecular patterns, the body’s immune system
can distinguish itself from these foreign substances and can
discriminate potentially harmful from nonharmful agents. In
addition, it can defend against abnormal cells and molecules
that periodically develop. The skin and its epithelial layers in
conjunction with the body’s normal inflammatory processes
make up the first line of the body’s defense and confer
innate
or natural immunity
to the host. Once these protective bar-
riers have been crossed, the body relies upon a second line
of defense known as the
adaptive immune response
to eradi-
cate infection by invading organisms. The adaptive immune
response develops slowly over time but results in the develop-
ment of antibodies capable of targeting specific microorgan-
isms and foreign substances should a second exposure occur.
This chapter covers immunity and the immune system,
including a complete discussion of innate and adaptive immu-
nity. Concepts related to key cellular function, recognition
systems, and effector responses integral to the immune system
are also presented. In addition, developmental aspects of the
immune system are discussed.
THE IMMUNE RESPONSE
After completing this section of the chapter, you should
be able to meet the following objectives:
••
Discuss the function of the immune system.
••
Contrast and compare the general properties of innate
and adaptive immunity.
••
Characterize the chemical mediators that orchestrate
the immune response.
THE IMMUNE RESPONSE
Cytokines and Their Role in Immunity
General Properties of Cytokines
Chemokines
Colony-Stimulating Factors
INNATE IMMUNITY
Epithelial Barriers
Cells of Innate Immunity
Neutrophils and Macrophages
Dendritic Cells
Natural Killer Cells and Intraepithelial Lymphocytes
Pathogen Recognition
Pattern Recognition
Toll-Like Receptors
Soluble Mediators of Innate Immunity
Opsonins
Inflammatory Cytokines
Acute-Phase Proteins
The Complement System
ADAPTIVE IMMUNITY
Antigens
Cells of Adaptive Immunity
Lymphocytes
Major Histocompatibility Complex Molecules
Antigen-Presenting Cells
B Lymphocytes and Humoral Immunity
Immunoglobulins
Humoral Immunity
T Lymphocytes and Cellular Immunity
Helper T Cells and Cytokines in Adaptive Immunity
Regulatory T Cells
Cytotoxic T Cells
Cell-Mediated Immunity
Lymphoid Organs
Thymus
Lymph Nodes
Spleen
Other Secondary Lymphoid Tissues
Active versus Passive Immunity
Regulation of the Adaptive Immune Response
DEVELOPMENTAL ASPECTS OF THE IMMUNE SYSTEM
Transfer of Immunity from Mother to Infant
Immune Response in the Older Adult
