PSYC 365: Week 3 - Psychoneuroimmunology

Psychoneuroimmunology (PNI)

The study of the relationship between psychological states and the functioning of the immune system

Psychology -> Nervous System -> Immunity

Immunocompetence

The extent to which one's immune system is functioning properly to ward off disease

Independent Variable in PNI research

1. Usually some psychological state

2. Naturally occurring or experimentally induced

Dependent Variable in PNI research

1.Usually a measure of immunocompetence

Measuring Immunocompetence

1. Enumerative Assay - Count cells for: Minimum number & Balance among type

2. Functional tests of immunity: Look at cells in action; can be In Vitro or In Vivo

In Vitro Tests for Immunocompetence

Functional tests performed outside the body, starts with a blood sample that is combined with a substance called mitogen, which is a substance that stimulates immune cell activity as though the cell were acting against an invading cell, or antigen.

In Vivo Tests for Immunocompetence

Functional tests inside the body, measure antibody (AB) production

Natural Killer (NK) Cell Activity

1. Measured by in vitro techniques

2. NK cell cytotoxic activity assay: test in which the proliferation and effectiveness of NK cells is measured after they have been exposed to diseased cells

3. NK cells lysis: Destroying tumour cells by exposing them to NK cells

In Vivo Tests with Herpesvirus

Suppression of the immune system increases herpesviruses which result in more antibodies (ABs). Therefore, higher AB counts for herpesvirus-specific antibodies indicate poorer immune system function

In Vivo Tests with Herpesvirus (Injection)

Introduction of an antigen into the body either by injection or nasal spray.

1. Count antigen specific antibodies in response to the injection

2. In this case, more ABs indicates better immunocompetence

Methodological Issues in PNI research

1. Short vs. Long-term effects

2. Many forms of immune-system function

3. Statistical significance vs. clinically important?

Stress & Immune Functioning

1. Acute Stressors: Immediately inhibit an effective immune system response. However, they can also enhance immune functioning

2. Personality: Affects stress response

3. Stress has Long-Term effects on immunity

Biological Embedding

The process by which experience has permanent effects on the expression of our genetic coding and, subsequently, on a range of biological processes this coding affects.

Early Childhood & Immune Functioning

Adverse experiences of early childhood impinge upon DNA and alters the immune system by permanently changing cells responsible for regulation of inflammation

Stress & URTI

1. Affected (worsened or started) by stress

2. Several factor's predict one's response to stress including: Generalized Anxiety Disorder, Social Support & Positive Life Events

Stress & URTI Research

1. Major life event often results in immunosuppression

2. Immunosuppression + Exposure to URTI = Increased likelihood of sickness

Stress & Autoimmune Disease

1. Stress can increase risk of contracting

2. Relaxation and meditation can lower pain in arthritis

Stress & Cancer

Stress can worsen cancer but not predispose someone to developing cancer. Often a result of psychological factors that affect NK cell activity under stress, NK cells, which protect against cancer.

Depression & Immune Functioning

1. Worsens immune functioning

2. Increased mortality risk for all patient

3. Possible immunosuppression: sIgA could explain immune-mood fluctuation

Negative Mood & Immune Functioning

High State negative affect associated with compromised immune systems (bi-directional)

Depression & Heart Health

1. Depression as possible risk factor for heart disease & related mortality

2. Higher risk of first heart attack

3. Higher risk with MDD

4. Associated with reduced responsiveness of the immune system, reduced ability to deal with inflammation

Negative Mood & HIV

Depression associated with lower T-helper cell activity in HIV+ individuals when T-helper cells count are high

Proposed Biological Mechanisms

Psychological states and traits affect our health and illness via:

1. Endocrine: Glucocorticoids

2. Sympathetic Nervous system: Reactivity hypothesis

3. Immune system: Affected by cortisol and activation of HPA axis

4. Behaviour (e.g., depression affects sleep)

HPA Axis

Chronic activation from stress can result in inflammation. Can result in pervasive negative effects.