Is the Function of the Immune System only to Protect?

Any theoretical analysis of the immune system must make assumptions about its function. The almost universal assumption among immunologists is that the sole function of the system is to protect but over the past quarter century there have been occasional claims that the system also has generative functions. This paper puts the human immune response into an historical context to show that the protection that the system provides is primarily against opportunistic pathogens. Since humans organized themselves into societies until the end of the nineteenth century they have been subjected to continuous decimation by infectious agents, both as endemic disease and epidemics of catastrophic proportions. The changes in society brought about as a result of industrialization and the introduction of modern sanitation measures have been the primary reasons for the control of infectious diseases in the industrialized nations. The tragic lesson of the AIDS epidemic is that in the presence of adequate public health and antibiotics, the immune system is necessary for the defense against infections by opportunistic pathogens. It is of course possible that this is the sole function of the immune system, and if it is, theorists must be skeptical of data and conclusions from experiments designed with the large doses of highly antigenic material because these may not be examining the response as it functions in nature. Similarly, for reasons discussed in the paper, theorists and experimentalists should look to other functions of the immune system. These generative functions mayserve in growth and differentiation of the organism.