Book excerpt: This book contains twelve chapters contributed by prestigious international experts who are at the forefront of B cell research, and aims to provide a cutting-edge and comprehensive overview of all aspects of B cells, including B cell development, maturation and activation, germinal center reaction, memory and plasma cell differentiation, and antibody-mediated positive and negative regulation of humoral immune responses. There are also three chapters describing human diseases caused by B cell abnormalities, including primary antibody deficiencies, autoimmune diseases, and B cell malignancies. We hope that this book will become a standard and routine reference for both basic researchers and clinicians.