This volume of Current Topics in Microbiology and Immunology was planned in parallel with an EM BO workshop on cell-cell Interactions in Leukocyte Homing and Differentiation held at the Basel Institute for Immunology in November 1992, and many of the workshop speakers have contributed to it. Cell adhesion is one of the most dynamic fields of biological research and presented in this book is the current knowledge on the structure and function of the major families of cell adhesion molecules-the integrins, the selectins, the immunoglobulin superfamily, and CD44. Complex interactions between the members of these families mediate diverse adhesion functions, including leukocyte-leukocyte interactions, lymphocyte homing, inflammation, and lymphocyte-stromal cell interaction during hematopoiesis. A great deal of emphasis is placed on the regulatory elements that control the expression and function of adhesion molecules. Cytokines not only induce the expression of certain adhesion molecules, but may also modify their functional status. For instance, the integrins exist in either an inactive nonfunctional form or an active functional form, and a number of intracellular or extracellular stimuli modify integrin function. This is particularly important during leukocyte binding to endothelium and transendothelial migration, which proceeds through a cascade of adhesion events. Although cell adhesion molecules play an important role in many processes, this book concentrates on their role within the immune system. A number of chapters discuss the migration of lymphocytes between hematopoietic organs such as the thymus, lymph nodes, Peyer's patches, and spleen.

The Dominance of Antigen-Specific Receptors in Antigen-Specific Immune Responses.- I Adhesion Molecules.- Integrins and Their Ligands.- Platelet Endothelial Cell Adhesion Molecule (CD31).- CD44: A Multitude of Isoforms with Diverse Functions.- The Selectins and Their Ligands.- II Regulation of Leukocyte-Endothelial Cell Adhesion.- A Model of Leukocyte Adhesion to Vascular Endothelium.- Regulation of Adhesion Receptor Expression in Endothelial Cells.- Regulation of Leukocyte Recruitment by Proadhesive Cytokines Immobilized on Endothelial Proteoglycan.- III Lymphoid Cell Homing Mechanisms.- Migration of Activated Lymphocytes.- The Peyer's Patch Homing Receptor.- Pro-T Cell Homing to the Thymus.- Quantitative Analysis of Lymphocyte Fluxes In Vivo.- Lymphocyte Recirculation and Life Span In Vivo.- IV Leukocyte Homing to Inflamed Tissues.- The Contributions of Integrins to Leukocyte Infiltration in Inflamed Tissues.- Regulation of Adhesion and Adhesion Molecules in Endothelium by Transforming Growth Factor-?.- Transendothelial Migration.- V Adhesion Molecules in Differentiation and Activation of Lymphocytes.- CD44 and Other Cell Interaction Molecules Contributing to B Lymphopoiesis.- CD4, CD8, and CD2 in T Cell Adhesion and Signaling.- Activation and Inactivation of Adhesion Molecules.