The Legacy of Sickness Behaviors.

Keith W Kelley,Stephen Kent

doi:10.3389/fpsyt.2020.607269

Abstract

Systemic infections of all types lead to a syndrome known as sickness behaviors. Changes in the behavior of febrile humans and animals formed the original basis for this concept. Body temperature is behaviorally regulated in both endotherms and ectotherms. However, infections cause other changes in body functions, including sleep disruption, anorexia, cognitive and memory deficits and disorientation. The brain mediates this entire cluster of symptoms, even though most major infections occur outside the brain. The true importance of sickness behaviors is not the numerous discoveries of symptoms that affect all of us when we get sick. Instead, the legacy of 30 years of research in sickness behaviors is that it established the physiologic importance of reciprocal communication systems between the immune system and the brain. This conceptual advance remains in its infancy.

Highlights

Lipopolysaccharide (LPS) is composed of a lipid and a polysaccharide expressed on the outer membrane of Gram-negative bacteria
Following the discovery that LPS acts as an adjuvant to enhance antibody responses, graduate students who studied immunology in the 1960s, 70s, and ‘80s were taught that the main target for LPS is B lymphocytes
This ignored the much earlier discovery in 1888 that injection of heat-killed gram-negative bacteria into rabbits causes fever. This simple example exemplifies the dichotomy in the relationship between studies in immunology and systemic physiology that continued until the end of the twentieth century

Summary

The Legacy of Sickness Behaviors

Reviewed by: Jan Pieter Konsman, Center National de la Recherche Scientifique (CNRS), France Manfred Schedlowski, University of Duisburg-Essen, Germany. Specialty section: This article was submitted to Psychopathology, a section of the journal Frontiers in Psychiatry. Infections cause other changes in body functions, including sleep disruption, anorexia, cognitive and memory deficits and disorientation. The brain mediates this entire cluster of symptoms, even though most major infections occur outside the brain. The legacy of 30 years of research in sickness behaviors is that it established the physiologic importance of reciprocal communication systems between the immune system and the brain. This conceptual advance remains in its infancy

INTRODUCTION

Something From the Immune System Increases Glucocorticoids in Blood

Thermoregulatory Behavior Formed the Basis of the Concept of Sickness Behavior