1 Department of Pediatrics, Georgetown University Medical Center, Washington, D.C.
Before describing the effects of chemicals on the immune system and projecting implications for pediatricians and for future research, I should like to review briefly the development of the immune system.
EVOLUTION OF THE IMMUNE SYSTEM
The system may be considered a series of adaptive mechanisms to an ever changing and hostile environment. At the "macro" level, the inductive influence was posed at the species; we refer to this process as phylogeny. Development of the immune system within the individual involves the cellular or microenvironment, and is referred to as ontogeny. Cellular responses (antigens) to the microenvironment result in the production of antibody or delayed hypersensitivity, and we refer to this phenomenon as the immune response.
Increasing pollution of our environment must be viewed against this changing role of the immune system. In phylogeny, the system began as unicellular responsesphagocytosis in the simplest of the invertebratesand, with constant changing of the macroenvironment, other cell types developed in the sponges and worms. Next, in the most primitive of vertebrates, one sees the beginnings of an early macroglobulin. Still further changes in the environment brought the development of gamma G of low molecular weight. In rodents, a species equipped to suckle their young, one sees secretory gamma A. Finally, one sees in man the development of five major classes of immunoglobulin as well as other serological defenses. As development has progressed, there has not been deletion of primitive responses. Instead we have added to them. We still perform the basic functions of phagocytosis in a greatly enhanced fashion.