Ganong's Review of Medical Physiology, 23rd Edition

Immunity, Infection,
& Inflammation
OBJECTIVES
After studying this chapter, you should be able to:
■ Understand the significance of immunity, particularly with respect to defending
the body against microbial invaders.
■ Define the circulating and tissue cell types that contribute to immune and inflammatory
responses.
■ Describe how phagocytes are able to kill internalized bacteria.
■ Identify the functions of hematopoietic growth factors, cytokines, and chemokines.
■ Delineate the roles and mechanisms of innate, acquired, humoral, and cellular immunity.
■ Understand the basis of inflammatory responses and wound healing.
INTRODUCTION
As an open system, the body is continuously called upon to
defend itself from potentially harmful invaders such as bacteria,
viruses, and other microbes. This is accomplished by the
immune system, which is subdivided into innate and adaptive
(or acquired) branches. The immune system is composed of
specialized effector cells that sense and respond to foreign
antigens and other molecular patterns not found in human
tissues. Likewise, the immune system clears the body’s own
cells that have become senescent or abnormal, such as cancer
cells. Finally, occasionally, normal host tissues become the
subject of inappropriate immune attack, such as in autoim-
IMMUNE EFFECTOR CELLS
Many immune effector cells circulate in the blood as the white
blood cells. In addition, the blood is the conduit for the precursor
cells that eventually develop into the immune cells of
the tissues. The circulating immunologic cells include granulocytes
(polymorphonuclear leukocytes, PMNs), comprising
neutrophils, eosinophils, and basophils; lymphocytes; and
C H A P T E R
3
mune diseases or in settings where normal cells are harmed as
innocent bystanders when the immune system mounts an
inflammatory response to an invader. It is beyond the scope of
this volume to provide a full treatment of all aspects of modern
immunology. Nevertheless, the student of physiology
should have a working knowledge of immune functions and
their regulation, due to a growing appreciation for the ways in
which the immune system can contribute to normal physiological
regulation in a variety of tissues, as well as contributions
of immune effectors to pathophysiology.
monocytes. Immune responses in the tissues are further amplified
by these cells following their extravascular migration,
as well as tissue macrophages (derived from monocytes) and
mast cells (related to basophils). Acting together, these cells
provide the body with powerful defenses against tumors and
viral, bacterial, and parasitic infections.
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