production of plasma cells and memory B cells can be divided into three broad stages: generation of mature, immunocompetent B cells(maturation), activa- Initial Contact between b and T cells tion of mature B cells when they interact with antigen, and differentiation of activated B cells into plasma cells and memory B cells. In many vertebrates, ng humans B-Cell maturation and mice, the bone marrow generates B cells. This process

recognition by most T cells from recognition by B iction. In most cases, both th maturati vation of ma the involver diversity o CD4\ and CD class I MHC Activat Engagement of TcR by Peptide: MHC Initiates interaction of th n antigenic Signal Transduction tide displayed though the sp

the B-cell rec and diffict Interaction of aB TCR with Class II MHC-Peptide Early Studies of the T-Cell Receptor complex cel aB and yo T-Cell Receptors: Structure and Roles ficity. Sec Organization and Rearrangement of TCR Genes gen alone by the major histo T-Cell Receptor Complex: TCR-CD3 erty precludes pur

that peptides derived from the antigen be displayed within the cleft of an MHC peptide-Mhcthe m ormation of the Antigen Processing for Presentation by Class I MHC Molecules Self-MHC Restriction of T Cells Class tides that Role of Antigen-Presenting Cells Evidence for Two Processing and Presentation Pathways

possesses a tightly linked cluster of genes. the ma jor products play roles in intercellular recognition and in dis on of vesicular Stomatitis Virus Peptide (top) Class I Molecule H-2K General Organization and Inheritance of the MHC MHC Molecules and Genes that Detailed Genomic Map of MHC Genes Cellular Distribution of MHC Molecules antigens of Regulation of MHC Expression implicated MHC and Immune Responsiveness natural killer

lecular association similar to an enzyme-substrate interaction, with an important distinction: it does not lead to an irreversible chemical alteration in either the antibody or the antigen. The association between an anti Fluorescent Antibody Staining Reveals Intracellular body and an antigen involves various noncovalent interac- tions between the antigenic determinant, or epitope, of the ntigen and the variable-region(vH/Vi) domain of the an- a Strength of Antigen-Antibody Interactions tibody molecule, particularly the hypervariable regions

Kappa Light-Chain Gene Rearrangement the vertebrate immune system is its ability to respond to an apparently limitless array of for eign antigens As immunoglobulin(Ig)sequence data accu- a Genetic Model Compatible with Ig Structure mulated, virtually every antibody molecule studied was found to contain a unique amino acid sequence in its vari a Multigene Organization

present on the B-cell membrane and secreted by plasma cells. Membrane-bound antibody con- fers antigenic specificity on B cells; antigen-specific prolifer- ation of B-cell clones is elicted by the interaction of membrane antibody with antigen Secreted antibodies ci culate in the blood, where they serve as the effectors of hu- moral immunity by searching out and neutralizing antigens or marking them for elimination. All antibodies share struc

cell receptor when complexed with MHC,are called antigens. The molecular properties of antigens and he way in which these properties ultimately contribute to immune activation are central to our understanding of the mmune system. This chapter describes some of the molecu- Complementarity of Interacting Surfaces of Antibody(left) lar features of antigens recognized by B or T cells. The chap and Antigen(rig ter also explores the contribution made to immunogenicity by the biological system of the host; ultimately the biological system determines whether a molecule that combines with a a Immunogenicity Versus Antigenicity Bor T cells antigen-binding receptor can then induce an im

body. These organs can be classified functionally nto two main groups. The primary lymphoid organs provide appropriate microenvironments for the development and maturation of lymphocytes. The secondary lymphoid organs rap antigen from defined tissues or vascular spaces and are sites where mature lymphocytes can interact effectively with that antigen. Blood vessels and lymphatic systems connect these organs, uniting them into a functional whole Carried within the blood and lymph and populating the Macrophage Interacting with