Overview

The immune system is a complex system of cells, organs and secretory agents that plays a key role in defence against pathogens, healing and communication with a large number of other systems in the body. It contains a large number of different cells, each with different functions, advantages and limitations, most of which secrete a dizzying variety of substances or cytokines that permit intercellular communication and which enhance or effect the cells' function. There are components of immunity that are primarily responsible for defence against pathogens, altered cells, or other foreign agents and there are components of the system that regulate inflammation and healing of wounds. Communication with nervous and metabolic systems is accomplished by other substances and structures. Many of these processes require coordinated collaboration among cells and substances and nearly all appear to be sensitive to internal rhythms and external events. In the rapidly growing field of psychoneuroimmunology (PNI), this complexity has added to the challenge of studying behaviour or central nervous system (CNS) interactions with the immune system (see also ‘Psychoneuroimmunology’).

In the face of the rapid growth of molecular biology and bioassay capabilities, PNI investigators now have access to a number of methods and measures that capture this complexity. In this chapter, we will review some of these newer approaches as well as some more traditional, widely used measures. Emphasis will be on what each measure tells us, how feasible and reliable it is and when it is appropriate.