24.1 Introduction 24.2 Clonal selection amplifies lymphocytes that respond to individual antigens 24.3 Immunoglobulin genes are assembled from their parts in lymphocytes 24.4 Light chains are assembled by a single recombination 24.5 Heavy chains are assembled by two recombinations 24.6 Recombination generates extensive diversity 24.7 Avian immunoglobulins are assembled from pseudogenes 24.8 Immune recombination uses two types of consensus sequence 24.9 Recombination generates deletions or inversions 24.10 The RAG proteins catalyze breakage and reunion 24.11 Allelic exclusion is triggered by productive rearrangement 24.12 DNA recombination causes class switching 24.13 Early heavy chain expression can be changed by RNA processing 24.14 Somatic mutation generates additional diversity 24.15 B cell development and memory 24.16 T-cell receptors are related to immunoglobulins 24.17 The major histocompatibility locus codes for many genes of the immune system