I. Physiology of the Immune
System
 The immune system consists of tissues, organs, and
processes that protect the body from invasion by foreign
material such as bacteria, viruses, and fungi. It also
removes worn-out or damaged cells from the body.
A. Organs of the Immune
System
 The immune system includes lymph (circulating fluid
that contains a type of white blood cell called
lymphocytes) and lymph nodes (interspersed oval
capsule structures) through which lymph circulates
(see Figure 6.1).
Health Psychology, 6/E by Linda Brannon and Jess
Feist
Copyright  2007 Wadsworth Publishing, a
division of Thomson Learning. All rights reserved.
A. Organs of the Immune
System
 Various types of lymphocytes include T-cells, B-cells,
and natural killer (NK) cells. The thymus, tonsils, and
spleen are also involved with the production,
maturation, or differentiation of the various types of
lymphocytes.
B. Function of the Immune
System
 The immune system is the body’s defense against foreign
invaders, and it must be virtually 100% effective in
destroying invaders (see Figure 6.2).
Health Psychology, 6/E by Linda Brannon and Jess
Feist
Copyright  2007 Wadsworth Publishing, a
division of Thomson Learning. All rights reserved.
1. Nonspecific Immune System
Responses
 Phagocytosis (attack of foreign particles by granulocytes
or macrophages) and inflammation (the sequence of
events that restores damaged tissue) occur with a wide
variety of invading particles.
2. Specific Immune System
Responses
 Contact with invading microorganisms sensitizes T-cells,
allowing the cytotoxic T-cells to subsequently recognize
these invaders and creating a specific immunity called cellmediated immunity.
 After coming into contact with an antigen, B-cells
differentiate into plasma cells that manufacture specific
antibodies that mark invading cells for later destruction
(see Figure 6.3).
2. Specific Immune System
Responses
 Even after the invaders have been destroyed, the immune
system keeps the critical information that allows future
manufacture of antibodies, creating immunity to an
invader that can persist for years (see Figure 6.4).
3. Creating Immunity
 Vaccination is the introduction of weakened or dead
bacteria or viruses, thus creating a specific immunity.
 Interferon, a protein produced by viral infection, may be
capable of producing a more general immunity to a
variety of viral infections, and recombinant DNA
research with interferon may enlarge the possibilities for
creating immunity.
C. Immune System Disorders
 Failures of the immune system leave a person open to
infection from viruses, bacteria, fungi, and parasites.
 The immune systems of some children fail to develop, and
acquired immune deficiency syndrome (AIDS) destroys
the immune systems of adults and children.
C. Immune System Disorders
 Allergies are the result of overactive immune systems,
and autoimmune diseases result when the immune
system fails to distinguish body cells from invaders and
starts to attack and destroy body cells.
 The immune surveillance theory hypothesizes a critical
role for the immune system in the development of
diseases. With cancer, for example, the immune system
fails to control the proliferation of cancerous cells.
II. Psychoneuroimmunology
 Psychoneuroimmunology is the interdisciplinary field
that focuses on the interactions among behavior, the
nervous system, the endocrine system, and the immune
system.
A. The History of
Psychoneuroimmunology
 Until the 1960s, the immune system was thought to be
independent of the nervous system and uninfluenced by
behavior.
 In 1975, Ader and Cohen demonstrated that the immune
system could be conditioned, laying the foundation for
psychoneuroimmunology.
A. The History of
Psychoneuroimmunology
 One way that the nervous system and immune system
communicate is through cytokines, chemical messengers
secreted by the immune system.
B. Research in
Psychoneuroimmunology
 Research in psychoneuroimmunology has attempted to
reveal the interactions among behavior, the nervous
system, the endocrine system, and the immune system by
demonstrating that behavior can affect the immune system
and that disease can result from these effects.
B. Research in
Psychoneuroimmunology
 Research has demonstrated that behavior can depress
immune system function, and a growing body of research
has linked lowered immune system function and
subsequent disease.
 Depression of the immune system appears to be easier
than enhancement of the immune system’s functioning.
B. Research in
Psychoneuroimmunology
 Research in psychoneuroimmunology should also
demonstrate that behavior affects immune system
functioning and that such impaired immune function
causes disease. A substantial body of research has
demonstrated the link between behavior and depressed
immune function and also between lowered immune
function and disease.
B. Research in
Psychoneuroimmunology
 Most studies in psychoneuroimmunology have
demonstrated that behavior can suppress immune system
function, but a few studies have used behavioral
interventions to attempt to boost immune system function.
C. Physical Mechanisms of
Influence
 The link between behavior and depressed immune
function must occur through some physical mechanism,
and research has examined both the action of the
peripheral nervous system during stress and
neuroendocrine responses in the brain.
C. Physical Mechanisms of
Influence
 The immune system also signals the nervous system by
way of cytokines. Thus, the interrelationship between
nervous system and immune system is complex, with
many possibilities for mutual influence (see Figure 6.5).
III. Does Stress Cause Disease?
 Disease is caused by many factors, and stress may be one
of those factors. However, most people at risk from
stressful experiences do not develop a disease.
 Although stress and disease are related, stress does not
seem to be a major cause of either physiological or
psychological disorders.
III. Does Stress Cause Disease?
 Just as most smokers will not die of lung cancer, most
people who experience high levels of temporary stress will
not develop a disease.
 In addition, many people who become sick have not
experienced unusually high levels of stress immediately
prior to their illness.
A. The Diathesis-Stress Model
 Why does stress affect some people, apparently causing
them to get sick, while leaving others unaffected?
A. The Diathesis-Stress Model
 The diathesis-stress model offers a possible answer to
this question.
 This model suggests that some individuals are
vulnerable to stress-related diseases because either
genetic weakness or biochemical imbalance inherently
predisposes them to those diseases.
A. The Diathesis-Stress Model
 Whether inherited or acquired, the vulnerability to
stress-related disease is relatively permanent.
 For people with a strong predisposition to a disease,
even a mild environmental stressor may be sufficient to
produce an illness episode.
B. Stress and Disease
 Some evidence exists concerning the link between stress
and headache, infectious disease, cardiovascular disease,
diabetes mellitus, premature birth, asthma, and rheumatoid
arthritis.
 In addition, stress shows some relationship to negative
moods and mood disorders such as depression and
anxiety.
1. Headaches
 Headaches are a common experience, but most do not
require medical attention.
 Of those that do, tension and migraine headaches are the
most common, and stress is a factor in both.
 Daily hassles are more important than life events in
producing chronic headaches, and research shows that
vulnerability and stress interact to produce headaches.
2. Infectious Disease
 Early research indicated that stress was a weak factor in
developing infectious disease.
 However, later research by Sheldon Cohen and his
associates intentionally exposed people to respiratory
viruses and found that those who were the most stressed
prior to the exposure were the one's who were most likely to
develop an infectious disease.
3. Cardiovascular
Disease
 Cardiovascular disease has a number of risk factors, some of
which are related to stress.
 For people with preexisting CVD, stress increases their risk
of heart attack.
 A large international study identified several psychological
stressors as a risk for heart attack; these risks included
workplace and home stress, financial problems, major life
events, depression, and external locus of control.
a. Hypertension


The relationship between stress and temporary increases in
blood pressure is stronger than the evidence for stress as a factor
in chronic hypertension.
Some evidence exists showing that chronic stress may be related
to hypertension, but other factors, such as sodium intake, may
interact with stress to raise the risk for hypertension.
b. Reactivity




Reactivity is the tendency for some people to react more strongly
than other people to stress.
Reactivity is a stable characteristic in some people, with blood
pressure, heart rate, and other biological responses used as
indexes of reactivity.
Educational level, socioeconomic level, and ethnic background
all relate to reactivity, putting those with low educational and
income levels and African Americans at increased risk for heart
disease and stroke.
Discrimination and stereotype threat may be factors that affect
the reactivity of African Americans, increasing their
vulnerability.
4. Other Physical Disorders
 Stress may be implicated in the development and
management of Type 1 and Type 2 diabetes mellitus and
rheumatoid arthritis. Stress experienced by pregnant
women increases the chances of premature delivery.
 Stress may contribute to the development of asthma
through effects on cytokines involved in inflammation.
4. Other Physical Disorders
 Rheumatoid arthritis is an autoimmune disorder, and
stress contributes to this disorder in both direct and
indirect ways.
C. Stress and Psychological
Disorders
 Stress is also related to several psychological disorders in
ways that the diathesis-stress model predicts: Some people
exposed to stressors develop these disorders, whereas
most do not.
 Research has also suggested that cytokines in the immune
system play a role in mood and the development of
psychological disorders.
1. Depression
 Stress is one factor that makes people vulnerable to
depression, but effective coping protects against depression.
 The tendency to ruminate over negative events increases the
risk for depression, and genetic vulnerability is also a risk.
1. Depression
 Chronic workplace stress, poor health, and caregiving are
stressors that increase the risk for depression.
 The route through which stress may produce depression is
through the effect on proinflammatory cytokines produced
by the immune system, which is related to the development
of depression.
2. Anxiety Disorders
 Anxiety disorders include panic attack, agoraphobia,
generalized anxiety, obsessive-compulsive disorders,
and posttraumatic stress disorder (PTSD).
 PTSD is, by definition, related to stress, and PTSD also
produces suppression of the immune system.
 Stress is less clearly related to the other anxiety
disorders, partly because the overlap between anxiety
and depression makes it difficult to disentangle these
two problems.
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I. Physiology of the Immune System