It can be seen that the insects are the still attracting most research and researchers. However, an increasing interest is emerging to study new invertebrate groups, especially those where the genome is known. Even though Drosophila has been and still is an excellent model for immune studies, it is now clear that there are great differences between immune responses in Drosophila and that of several other invertebrates, which indeed calls for more research on other invertebrates

Invertebrate Immunity: Mechanisms of Invertebrate Vector-Parasite Relations consists of chapters presented at a workshop on invertebrate defense mechanisms, sponsored by the National Institutes of Health and held in Bethesda, Maryland, on April 17 and 18, 1974. Organized into four parts, having a total of 24 chapters, this book first discusses the barrier imposed by the gut of invertebrates to invading parasites. It then centers on the role of invertebrate hemocytes and other phagocytic cells in immunity, as well as the humoral defense mechanisms of these organisms. Other topics discussed include parasite encapsulation in insects, role of melanin in host-parasite interaction, and use of host hormones by insect parasites to make the host environment favorable for their growth and development. This book will be essential for those interested in comparative immunology and in invertebrate immune responses. It will be of special interest to entomologists, protozoologists, physicians, veterinarians, ecologists, pathologists, research workers, science teachers, and graduate students.

The biological bases of invertebrate immune responses have interested scientists for decades, from the first relevant observation by E. Metchnikoff in 1882, who discovered phagocytosis while studying starfish larvae. Invertebrate immunology first began to be appre ciated as an important field in the late 1960s and 1970s. However, in the following years there was much controversy regarding the question: do invertebrates offer insight into the origin of the sophisticated immune responses of the vertebrates? There are several reasons why progress in research on invertebrate immune competence has been painfully slow. One of the main impediments to the progress, as compared to the fast development of knowledge in the vertebrate systems, was the fact that most of the studies concentrated on "whole organism" assays, mainly on grafting tissues between allogeneic partners. Only in the last few years have more and more aspects of invertebrate immunity been investigated on the cellular, biochemical and molecular levels. These studies led to discoveries of novel defense reactions, new pathways of effector mechanisms which are elicited after recognition of "nonself', and complex, sometimes highly polymorphic genetic elements that control invertebrate immune reactions. The importance of invertebrate immunity for understanding "immunology" as a whole, despite the conflicting models and hypotheses, is now much more recognized than before. Although most of the 20 phyla belonging to the inver tebrates have different modes of life, body organizations, habitats occupied, and biochemical patterns, they show striking aspects of exceptional precision for discriminating between self and nonself.

E. L. Cooper The Immunodefense System Because invertebrates are exceedingly diverse and numerous, estimates reveal nearly 2 million species classified in more than 20 phyla from unicellular organisms up to the complex, multicellular protostomes and deuterostomes. It is not surprising to find less diverse defense/immune responses whose effector mechanisms remain to be completely elucidated. Of course, I am not advocating that the few of us devoted to analyzing invertebrate immunity attempt the Herculean task of examining all these species to uncover some kind of unique response! As these two volumes will reveal, we are doing fairly well in examining in depth only the most miniscule examples of invertebrates, some of which have great effects on human populations such as edible crustaceans or insect pests. This is in striking contrast to the mass of information on the mammalian immune response which has been derived essentially from the mouse, a member of one phylum, Vertebrata, an approach, reductionist to be sure, but one that has served well both the technological and conceptual advances of immunology as a disci pline. The essential framework of immunology, the overwhelming burst of results since the 1960s, have emanated primarily from this single animal. We should not forget the thymus and the bird's bursa of Fabricius, without which we might have been slower to recognize the bipartite T /B system.

E. L. Cooper In Volume 23 we considered, in seven chapters, the basic armamentarium of the invertebrate immune system and its cells, as well as an analysis of antigens, setting the stage for the initiation of an immune response. We studied cell products, natural or induced, as revealed by nonspecific and specific responses following antigenic challenge such as the pro phenol oxidase system, the lytic responses, the Ig superfamily, and the place this family offers invertebrates and insect hemolymph proteins as candidates for membership. At this point, these various topics seemed to converge, almost to overlap, in some instances, presenting a challenge as to how to move from one subject to another. Chapter 1, in this volume offers the bridge to Volume 23 and its final Chapter 7. This Volume 24 contains contributions pertaining to cell activities and the environment. Chapters 1-4 refer specifically to interactions between cells and the integration of cell activities. The focus is on a functional immune system, with antigenic challenge as a subtopic. In Chapters 5-7, the environment is considered from several points of view and the main subtopic here is the result of the consequences of connections and missed signals. The internal and external environments are treated, revealing what may happen when normal immune responses are interfered with. All this is integrated by the consideration of the three great regulatory systems, the ever-present network that somehow acts as the monitor or control for all incoming and outgoing signals.