I’m Not Sick

I’m Not Sick is a personal account concerned with the immune system. This is the body’s defense system of molecules, cells, tissues and organs that are responsible for preventing infections against external pathogenic microorganisms such as viruses, bacteria and parasites. The body’s immune system is also considered to be a surveillance system that helps us guard against developing uncontrolled cell division that may develop into cancer. The greatest portion of scientific research concerns the immune system of humans. However there are a growing number of immunologists who are pure researchers interested in how the immune system developed to its present state and not so unique in humans. Thus to understand how the immune system evolved, an international group called, comparative immunologists, analyzes immune systems in a variety of more primitive animal models than humans, (Besides the ethical and moral concerns slows considerably or even curtails and prevent extensive experimentation on human subjects). We examine the immune systems of extremely valuable invertebrate animals such as nematode worms, fruit flies, snails, crabs, crayfish, earthworms, sea urchins and tunicates. Some of these animals are beneficial economically, well known as sources of food whereas others are pests and outright threats as vectors and intermediate hosts of parasitic diseases. Among the vertebrates, we also examine the immune systems of equally important sharks, zebra fish, trout, catfish, frogs, snakes, lizards, chickens and mostly mice among mammals. With the exception of mice and chickens, the other animal models are inexpensive and less controversial to maintain and therefore advantageous with respect to sources of research funds. By examining the immune systems of these animal models in research labs around the world, in universities, governmental labs and private research institutes, we have discovered molecules and mechanisms that are similar across the animal and even the plant kingdoms. Primitive animals have inhabited the earth for millions of years and this fact alone is strong evidence that they have evolved an efficient survival strategy, one of which is the immune system. For without an effective means of fighting potentially infectious and deleterious pathogens, our earth would not be inhabited by such an enormous array of animals with respect to sheer numbers and species as we have today. This list is staggering, almost impossible to fathom especially among the insects. To be less anthropocentric, we humans must recognize and acknowledge that we are clearly not alone on this planet. We can benefit by observing and seriously considering how our animal cohorts have succeeded in one aspect of existence common to all of us: to live a normal life span relatively free of infection and disease. We have gained much by examining the immune system from the comparative viewpoint. Ellie Metchnikoff, a Russian zoologist discovered phagocytosis in marine animals and advanced causes explaining the importance of cells, especially certain leukocytes in the body’s defense against infection. Then during the latter part of the 19th century, mostly at the Pasteur Institute in Paris, immunologists mostly believed in the supremacy of the humoral system, now known to be concerned with antibodies. Metchnikoff’s simple finding, coupled with his prescience and steadfast insistence, therefore split the prevailing monolithic field of immunology into two independent camps the cellular and humoral which still exists today. Second, without Metchnikoff’s observation, we may have progressed slower with respect to discovering the mammalian equivalents of the body’s sites that control production and output of cells primarily responsible for cellular and humoral immunity: the thymus and bursa of Fabricius in birds and the thymus and bone marrow in mammals. Third, immunology seems to be returning to the original impetus that was sparked one hundred years ago, reaching back to the invertebrates, defining and refining the deeper, more molecular mechanisms that govern immune response signaling. Fourth, and perhaps of more immediate importance, such insights now point to possible sources of therapy for certain microbial diseases that have become uncontrolled under the influence of currently synthesized antibiotics. At the very outset it is well to point out as clearly as possible certain distinctions that may exist between what are in many instances similar terms or variations on those terms. The term “comparative immunology” seems to rest immutable just as comparative religion, comparative anatomy, comparative biochemistry, comparative physiology and comparative endocrinology over the years variations on comparative immunology have cropped up and perhaps caused some confusion even among those of us who work in the field. What comparative immunology is not is a study of the ontogeny of the immune system as is often the designation of our place at large international congresses of immunology or is the perception of immunologists with minimal education in the classical biological sciences. In like manner, comparative immunology in “sensu strictu” is not developmental immunology that on the one hand is a broad designation while on the other; it can be restricted to “ontogeny” or embryology. What comparative is can be embodied in the terms “evolution” and ”phylogeny”, designations related to the gradual becoming, in the group sense or taxonomic sense, of the immune system. By comparing phenomena or mechanisms in various taxonomic groups or crucial representatives in those groups, immunologists arrive at a more complete picture of how the immune system emerged in a step wise, perhaps even logical sequence, at least as far as current immunologic theory and dogma will allow. Another way to view the breadth of phylogenetic studies of immunity is to bring together, coherently, diverse observations into an evolutionary picture which will provide an acceptable view of the mechanisms underlying how immunologically competent cells and the molecules that they synthesize and secrete, underwent functional diversification. In a concern for the phylogeny of immunity, there must of course be a clear understanding of the phylogeny of the animal kingdom. After considering it, one becomes sharply conscious with respect to the staggering array of the many complex and diverse species on earth. Then, what quickly comes to mind is the question that concerns the mechanism by which all these species evolved.