Come Together

sors. Unfortunately, the cytokine appears not to influ-traction, hydrogen bonding, hydrophobic packing, and shape and charge complemetarity, have been known to ence B lymphopoiesis in humans and no factor with be important in protein-protein interactions for decades. comparable function has been found. There are also Other, less ubiquitous and more evasive, factors, such dramatic species differences in expression of the en-as allostery, cooperativity, and plasticity, have also been zyme TdT during human, but not murine fetal life. This identified as important influences on protein-protein has important consequences for the diversity of lympho-recognition. While the advent of recombinant protein cyte antigen receptors at birth, and we should be reproduction , site-directed mutagenesis, and sophisti-minded that our experimental models have limitations. cated techniques for determining the energetics of pro-One of the attractive aspects of immunology is the fact tein binding have made it possible to begin to dissect that strongly held opinions are frequently demolished by each of these influences individually in model protein new data. While this is a good thing for the experimental-interaction systems, the facile extension of these find-ist, it creates a challenge for textbook authors. Schemes ings to the entire spectrum of protein-protein interac-for early stages of lymphocyte differentiation shown in tions has commonly been wrought with pitfalls. The rea-this book are already being questioned and other " likely " sons for this conundrum are likely to be as numerous and scenarios will fall with further study. Fortunately, tables complex as the factors that influence these interactions, from the book will be available and frequently updated perhaps not the least of which is what appears to be on a web site. It would have been even better if this the inherent messiness of biology which, relative to terrific idea were extended to many of the 156 figures fields such as physics, presents a paucity of general in this volume. theories and overarching laws. Further confounding the Throughout the text, the author treats us to many issue is that we seem to be expanding the list of rules amusing metaphors. For example, we learn about lym-that govern these interactions at least as quickly as we phocyte precursors that are not " truly committed in an are understanding those that have been on the list for so irreversible Calvinistic sense. " Immature self-reactive B long. Realizing, for example, that two interface hydrogen cells are " given an opportunity to reform …