Immunology: how it all began

Origin and Evolution of the Vertebrate Immune Systemedited by L. Du Pasquier and G.W. LitmanSpringer-Verlag, 2000. £117.00 (326 + x)ISBN 3 540 66414 9With the recent sequencing of the entire human major histocompatibility complex (MHC), and several recent volumes devoted exclusively to MHC evolution, Origin and Evolution of the Vertebrate Immune System provides a welcome broad perspective on diverse aspects of mammalian and non-mammalian immune systems.Appropriately, the book begins with three perspectives on invertebrate immunity focusing on genomic approaches to sea urchin immunity, antimicrobial defense in Drosophila and invertebrate complement systems. It devotes a chapter to the latest insights on MHC evolution from the perspective of genome and chromosome paralogy and to a review of lymphoid-like and hematopoietic cells of basal vertebrates such as cyclostomes and the bichir, a primitive bony fish.The role of RAG genes in the saltational evolution of the immune system is reviewed, as is the phylogenetic diversity of antigen receptors, including MHC, T-cell receptor (TCR) and immunoglobulin (Ig). The structure and evolution of Ig genes is covered in several chapters, as is the immunogenetics of sharks – the most ancient lineage to exhibit the full diversity of molecular receptors by which the adaptive immune system is defined. The book ends with chapters on somatic diversification of Ig light chains and a discussion of the evolution of TCR signal transduction units, based largely on recent studies of chicken CD3 genes.The volume goes far beyond the modern, narrow interpretation of ‘evolution’, which often implies an overabundance of phylogenetic gene trees and endless comparisons of DNA sequences. Throughout, it takes a rigorous cellular and molecular approach to the diversity of receptor molecules and their expression in both vertebrates and invertebrates. The result is a useful synthesis of a vast array of work scattered across the scientific literature, and an exciting cross-section of disciplines and approaches. For example, in the first chapter by J.P. Rast and colleagues, we learn of the application of large-scale genomics approaches, such as screening of cDNAs in high-density arrays and bcterial artificial chromosome (BAC) cloning, to rapidly isolating and dissecting immunologically relevant genes from a model invertebrate, the sea urchin. Du Pasquier presents the results of new large-scale search for genes containing variable regions in a wide diversity of metazoans, including sponges, arthropods and nematodes. E. Bengten, T. Ota and colleagues review the evolution and diversity of Ig light chains. J.D. Hansen and J.F. McBlane review the fascinating story of the origin of vertebrate RAG genes via a transposition event and the key roles that RAG-mediated transposition probably played in the origin of TCR and Ig adaptive immunity.With the huge diversity of genes and proteins discussed in this volume, researchers on both vertebrate and invertebrate immunology will all find something of interest. And, as Phase I of the genome projects draws to a close, Phase II – comparative genomics – will inevitably expand our view of the origins of vertebrate immunity. This volume is a worthy prelude to that second phase and offers a glimpse of some of the excitement to come.