Molecular epidemiology: principles and practices. Schulte PA, Perera FP, eds. San Diego, CA: Academic Press, 1993 Apr; :407-442
The mammalian host defense system is a complex network of cells and mediators with recognition and response functions throughout most tissues of higher organisms. The primary functions of the host defense system are repairing injured tissue, identifying and removing foreign substances, destroying or containing infectious agents, and, in some cases, eradicating cancer cells. These functions are carried out through both nonspecific mechanisms of innate or natural immunity and through specific mechanisms of acquired immunity that develops as the organism encounters environmental agents or antigens. The term "immune system" will be used to refer to all components of nonspecific innate immunity and antigen-specific acquired immunity, since their components and activities are invariably intertwined. Over the last few decades, the cellular and molecular basis for many host defense functions has been uncovered through the use of emerging laboratoty technologies. The use of these laboratoty methods to detect biologic markers in epidemiologic studies already has provided critical information in many areas of basic and public health science. Their future potential is even greater. However, this potential can be realized only by applying scientifically valid and logistically feasible markers in field studies. The absence of either characteristic can result in flawed or failed research through the use of markers that are not measured properly or cannot be interpreted with respect to exposure, susceptibility or health effects (NRC, 1992). This chapter outlines the major considerations involved in using laboratory tests for immune markers in epidemiologic studies. Although it cannot provide a complete description of the host defense system, for which many excellent texts and reviews are available (e.g., Hood et al., 1990; Roitt, 1990; Paul, 1992), it discusses many of the cellular and molecular components of the immune system and their use as biologic markers.