1. Lymphocytes

Lymphocytes are white blood cells uniform in appearance but varied in function and include T, B, and natural killer cells. These cells are responsible for antibody production, direct cell-mediated killing of virus-infected and tumor cells, and regulation of the immune response. Advances in immunology have led to the characterization of newly appreciated effector populations such as IL-17–producing T cells, T cells with regulatory function, and natural killer T cells, thus revising established paradigms. This chapter provides an overview of the major lymphocyte populations with emphasis on their development, distinguishing characteristics, and functions.

Key words: Lymphocyte, adaptive immune system, T cell, B cell, natural killer cell

Abbreviations used: APC, Antigen presenting cell, BCR, B-cell receptor, CSR, Class switch recombination, D, Diversity gene segment, DC, Dendritic cell, DP, Double-positive, GC, Germinal center, iNKT, Invariant natural killer T cell, ITAM, Immunotyrosine-based activation motif, J, Joining gene segment, NK, Natural killer, nTreg, Thymic-derived “natural” regulatory T cell, SHM, Somatic hypermutation, T_CM, Central memory T cell, T_EM, Effector memory T cell, TCR, T-cell receptor, Treg, T-regulatory cell, V, Variable gene segment